Quote - At #1: WinXP 64 bit drivers can be a problem. Not with nVidia though. 
I looked up the driver support on the Intel site. WinXP 64 is supported. As long as you don't put two graphics cards in Crossfire mode (an ATI feature, and thus badly supported under anything not Windows XP 32 bit) you're fine.
DVD burning - this could be troublesome. You should check out the major burning software brands - Nero and Roxio - for their XP64 support.
Virus scanners - usually crap on XP64. Though Housecall (online scanner by TrendMicro, www.trendmicro.com) works on my XP64 system.

At #2: actually, see the DVD remark of #1. The software bundled with the DVD writer might not be XP64 or Vista compatible. Another problem with most software bundled with retail versions is that they're the 'basic' or 'lite' versions, not the full fledged versions. Better go OEM and purchase the burning software YOU choose, with the features YOU want.

At #3: Totally agreed. And don't forget NEC - though some of their DVD burners tend to be a little noisy. Tip: try to get some info on the noise of a DVD player in a computer store by asking them tp play a demo movie in this box and that - if the DVD player sounds like a figher jet taking off you should consider another brand...

At #4: RAID 1 indeed only deals with physical drive failure. I'd also say not to bother too much with RAID 0. It only speeds up transfer rate, not access time, and most applications do not really benefit from the increased transfer rate. A notable exception would be harddisk recording.

Not using RAID 0 also allows you to fine tune what disks are used for what purpose. For example, it might be a good idea to place the Windows swap file on one disk and the Poser libraries on another.

At #5:

Thanks svdl!  VERY helpful info!

On the OS, I'm now thinking of going with XP Pro plus upgrade coupon for Vista (which seems to be zero incrementl cost anyway, at least on newegg).  I need to check into that a little more though since I think the version of Vista you get is the business version, which I think I saw somewhere is fairly limited.

On the DVD drive, I'm thinking of going OEM now since I already have burning software... and I assume I can get the proper drivers online somewhere if they aren't included.

Will look at the NEC burner too...

Interesting idea on task assignment to different drives!  I'm thinking of putting OS and all programs on one of my 320GB sata drives and using the second drive for all my personal stuff, including runtimes.  This would make it easier to set up backups I think.  As for the swap file, I guess I'd put that on the first drive with the system stuff.

Getting close to time to pull the trigger, so thanks again!