One thing I've always found on "tweaks".  Although many do not agree, Microsoft really knows what is best for Windows.  A lot of the tweaks that are found on the net either is "snake oil" (another name for what startabartfast mentions) or they are only for one specific problem with one specific PC's hardware and not really applicable to all.

Programs in the startup, for example, are another issue.  There can be (and usually areprograms that do not need to be in the startup.

sorry i have to disagree particularly with concern to laptops.

while win7 is by far the best OS and requiring far less tha prevous OS' early Xp and win98 required a boat load.

Scott, for a custom builder such as yourself, that is one thing.  For the masses and aftermarket, its another.  I get a lot of problem calls and many are "self inflicted" problems,  and some require on site work and even reinstallation because it was too far gone.  These include system "tweaks", along with other self inflicted problems such as running registry type programs that can screw up more than they claim to fix (and fall in the snake oil class). 

slartabartfast

 You are not the only one that has mentioned "disabling services". What is that exactly and what are you disabling.

A lot of the windows operating system are modules (small subprograms), called services, that run in the background, or just sit in memory waiting to be called to do their specific task. Not all of them are actually necessary for general use and many of them may not actually execute any useful operations during a session. Some people think they can radically improve their computer's performance by keeping unnecessary services from loading at all or disabling them after startup. Except for a few instances where a specific service might interfere with a particular application, this is a generally disappointing, and sometimes disastrous, enterprise. Most machines capable of running windows comfortably, can handle the standard services without any noticeable drag on performance.

Type "services" into your start menu "search for programs and files" box  and double click the "services" shortcut and you can see what is running on your machine. Some of these are essential to running anything at all, others will only come into play when needed. You can actually change the way they load, or keep them from loading pretty easily from this control panel applet. The trick is knowing which you can get away with killing, as some are critical.

http://www.blackviper.com/windows-services/

Being on an older machine with only 4GB of RAM, I've been using http://www.iobit.com/gamebooster.html (I have the older version of GameBooster) which basically puts a halt on all unnecessary background services and them uses those resources for Sonar (or whatever other software you run).
Although this is made for "gamers", I think it's quite useful for audio machines that are limited in RAM (like mine). 

fireberd


Scott, for a custom builder such as yourself, that is one thing.  For the masses and aftermarket, its another.  I get a lot of problem calls and many are "self inflicted" problems,  and some require on site work and even reinstallation because it was too far gone.  These include system "tweaks", along with other self inflicted problems such as running registry type programs that can screw up more than they claim to fix (and fall in the snake oil class). 

thanks that mad me laugh  i hear ya on the end user err errors and yeah the 3rd party reg programs argghghghg..
or installing norton everything even worse. 

I didn't read it but someone just started a thread in X2 form "slow after running CC cleaner" 
I did very little to W7 after install. But that's a "real" version and not an OME with bloatware. Most of the tweaking happens with the off the shelf computers, A custom built should not need much tweaking these days.  

I did a simple test while trouble shooting  DPCLAT latency on a laptop once. 

I installed Windows XP and ran the meter at each step of the way. Disabling process did nothing to the DPCLAT reading, But the wireless card and battery managment were huge.