A lot of people (including me) tend to forget about looking at seeing what is going on with the task scheduler.
Apps love putting in loads of entries here without any notification. Microsoft (among others) often leave tasks here you don't need to run.

If you are in doubt about disabling a task, Google it up.

Cheers

Alex

+1 to that, Alex
 
And I recommend digging deep, especially with Microsoft services - some of which do nothing but dialing home for things like customer experience feedback
 
I remember one weird occasion when we had a heavy work session with Sonar and all worked fine for 8 hours, but suddenly changed to getting drop-outs for no obvious reason ... and since this happened right after midnight I got a tip from a forumite to go check the remaining scheduled tasks - and bingo: there was one of these useless buggers that had awoken to disturb DAW peace ...
 
 

FreeFlyBertl
+1 to that, Alex
 
And I recommend digging deep, especially with Microsoft services - some of which do nothing but dialing home for things like customer experience feedback
 
I remember one weird occasion when we had a heavy work session with Sonar and all worked fine for 8 hours, but suddenly changed to getting drop-outs for no obvious reason ... and since this happened right after midnight I got a tip from a forumite to go check the remaining scheduled tasks - and bingo: there was one of these useless buggers that had awoken to disturb DAW peace ...
 
 

I have been there before. All of a sudden a windows update starts right in the middle of your recording session or the task scheduler starts a defrag process or something stupid like that.
 
Now I have a set of rules that resolves a bunch of problems. Before I start to record I take the time to disconnect from the internet. I disable windows update, task scheduler, security stuff and virus software. I disable useless third party programs that run in the background. like for example skype update apps.
 
When I am finished recording and I want to use the computer for other things I will enable all that stuff again. This practice has saved me a ton of headaches while using Sonar.

Being a PC tech, I keep a fairly "vanilla" system.  However, I do go through and disable the Ethernet NIC, stop other programs such as Malwarebytes, Logitech monitor, AMD Video helper, etc., before recording (or mixing).  After I'm done, I enable the Ethernet NIC and then restart the PC to bring everything back.
 
Another thing I do after I finish whatever recording/mixing, etc is to back up the project to a second hard drive.   

" I disable windows update, task scheduler,..."
How do you disable task scheduler (win 7) ?

fireberd
Being a PC tech, I keep a fairly "vanilla" system.  However, I do go through and disable the Ethernet NIC, stop other programs such as Malwarebytes, Logitech monitor, AMD Video helper, etc., before recording (or mixing).  After I'm done, I enable the Ethernet NIC and then restart the PC to bring everything back.
 
Another thing I do after I finish whatever recording/mixing, etc is to back up the project to a second hard drive.   

Hmmm..different strokes I guess, but I have zero issues with any of that. I also run a vanilla system with some tweaks, but I certainly have no need to go thorugh that rather irksome process..Of course, as always YMMV.

> I disable windows update, task scheduler, security stuff and virus software. I disable useless third party programs that run in the background. like for example skype update apps.
 
Windows update, task scheduler, security software, virus scanners all enabled. Everything works fine at my end. If it's configured correctly this functionality becomes your friend not your enemy. Internet works all the time as well.
 
All I have is DAW software running. Windows is optimal (unnecessary services and processes disabled) and it's probably taken days to get it that way. Every now and again I need to perform maintenance to keep it that way.
 
When I want to go into an environment for skype, office etc I reboot my machine and start another Windows operating system or whatever miles away from my DAW..
That's the killer, when you run third party apps beside your DAW like Word and Skype etc.

TS

" I disable windows update, task scheduler,..."
How do you disable task scheduler (win 7) ?

There are a few ways to do this. but perhaps the easiest way to do this in windows 7 is to go to start and in the search type msconfig. A window comes up with 5 tabs. There is a tab called services. These are all the services that run in the background when windows is operational. Some of those things the OS needs to function so be careful when you are in there and don't turn off anything if you don't know what it does!
 
task scheduler can be found in there. Just uncheck mark it. You can also uncheck mark windows update while your at it. You can also uncheck disk defragmenter. There is a box that says hide all microsoft services. Check that and only the third party services show and the microsoft services are removed from the list.
 
uncheck things like skype updater, google updater ect. These things run in the background and they look to see if there are updates for third party software.
 
The startup tab shows a list of all the programs that start when you turn on your computer. Some of these run in the background. Others display an icon to the bottom right next to the windows clock. turn things off like apple update ect. Don't turn off anything you think you might use. I keep the adobe on because Sonars manuals are in adobe pdfs and I may need to reference them.
 
When your done exit and reboot. That is it your done. Takes 15 minutes and now your ready to record music. When your done go back an enable everything again

Sorry few things I disagree with.....

Using msconfig to disable services or apps is not recommended at all. This is generally only used for troubleshooting purposes and not optimizing!
 
Before you remove or tweak anything check to see if you can remove some applications in you control panel first under "uninstall a program".
 
If you need services just go to control panel and search for services, or find it through administrative tools.
http://technet.microsoft.com/en-us/library/cc736564%28v=ws.10%29.aspx
 
As far as startup is concerned, once you are certain you can get rid of a process it is better to delete it rather than disable it (you could then audition with msconfig but google generally tells you all you need to know), I use ccleaner for this (although I've also been known to delete the registry keys myself, you really only need regedit, but that can be dangerous).... check here:
http://www.howtogeek.com/74523/
 
There are lots of methods but you should not use msconfig unless you are troubleshooting or doing something that is temporary.
 
If you want to see what is going on Process Monitor is highly recommended.
 
You should never disable the task scheduler , but you should check to see what tasks are actually running, and either remove or get them to run at more convenient times. There is some stuff there you want to run. More info:
 
http://blogs.technet.com/b/askpfeplat/archive/2013/07/15/why-you-shouldn-t-disable-the-task-scheduler-service-in-windows-7-and-windows-8.aspx
 
cc-Cleaner is also good at cleaning up the disk and the registry. Some people don't like cleaning up the registry, the reasons are valid enough, I can understand that, but I do it and have never had a problem.
 
Always update your drivers, always run windows update.
Finally defrag! and Run chkdsk often.
Every six months I recommend running sfc /scannow but that's not strictly necessary.
 
Check your event viewer often.
 
And have a backup/rollback strategy. !!!
 
BTW this takes a lot longer than 15 minutes.

Alex,
 
This sort of information for DAW tuning is so useful.  I wish there was a DAW tuning wiki (is there?) or something like that where the universe of knowledge for optimized DAW tweaking was available for the mortal user.
 
Can you imagine a DAW install/optimize utility that actually goes out and checks this stuff for you and makes recommendations and tweaks upon user approval?  I'm imagining it...