I'm in Australia so Jims a bit far away but I've used his consultancy service to provide a parts list of things that he knows work well together.

I'd go for a barebones ready-made system (i.e. a complete system but without an OEM licenced OS and all the bloat/guff that comes installed with it).  Then get yourself a single user Professional-level Windows licence, install and go.  Thing is, you can get a good barebones 'complete' system for less than buying the same set of components and building it yourself these days.

While I agree a custom or barebones system would be best/better (my system is self built), the specific Dell doesn't sound bad.  There's nothing wrong with an OEM operating system.  It is the same as a full retail version except the OEM version is only legally licensed for the system it was delivered with. 
 
I see posts here and on other recording forums of users with Dell's, HP's, etc and, from their posts, they are not having any recording issues with them.
 
 

The non-OEM licence gives you an easier time of upgrading the machine if you change various hardware components, although to be fair M$ are pretty reasonable about accepting re-activation requests for OEM systems whose hardware configuration has changed.  
 
Personally, I'd rather spend a few £££ more for a non-OEM licence then I don't have to worry at all about making modifications to the machine or even installing it on a new one but either choice has its good and bad points.

I purchased an OEM license for WinXP when I built my DAW back in 2007.  I had no trouble changing out the MB, processor and memory when my original MB failed.  I don't even think I had to call them.  I did keep the OS on the same drive, so I just moved the drives over.  I also had no trouble updgrading to WIN7 by installing the OS on a new drive with OEM version too.
 
I would not be too concerned with OEM versions, MS is pretty reasonable.

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If you have built in the past why not build again? It might cost a bit extra but it's money well spent and you'll know what you have.
 
Add an OS for around 100.00 american give or take depending on the version. I would do it and never look back.
 
I haven't had the time to finish it yet but I have started to put together a "how to" on building a computer yourself. I have full pics which I'll probably post to my website. Even better it'll be free. Tech moves so fast that by time I would sell it things will have moved on...so if you have reservations hang on a bit and I can give you enough info to get started on it. I'll post the info as I get it up ( the info that is).  You don't need the same hardware  I used since this will be a general guide.
 
There are also some great resources in Electronic Musician Magazine. Some of those articles walk you through all the hardware and build. One of my earlier builds was a copy of one of those builds.

Well I ended up going with the PCPartpicker as a parts list. I got everything from either NewEgg or Amazon, which got free shipping on everything (making up for the $5-$10 price difference on everything).
 
I've got it mostly built, just sorting out the modular power supply and cabling issues. I flashed my current C Drive onto an SSD so hopefully the headache will be minimal when I fire it up. Stay tuned for more.

Good luck!