My two cents..
First, on the build vs. buy.. I agree with everything that's been said on the cost of maintenance, etc. and have one thing to add: Standardization. When you buy a name-brand PC you're guaranteed to have everything be absolutely identical and you can usually get the same machine for a few months (especially with IBM/Compaq, Dell a bit less so). When you're dealing with 150+ PC's the only logical way to deploy them is to build a "gold" PC and take an image of it with Ghost or DriveImage, then burn that image onto the PC's your going to deploy. Every major company that I've ever seen deploys PC's in this manner - For example, the bank I work for has literally 500+ "gold" images for different needs - Branches, back offices call centers, this app, that app, etc. If something goes really bad, slap the boot disk in, have coffee and you've got a perfect working PC again. Clones can come close, but you're always going to end up with some oddballs - Different IRQ's here, some odd hardware conflict there, a different version on the video card BIOS that isn't compatible with the driver you've used other places, etc.
One last piece of advice.. Saying that "None of my users will ever need a 1Ghz+ or a 40 GB drive machine" is being a bit shortsighted. When Windows XP 2003 comes out the REQUIRES a 1 Ghz machine and 8 GB of drive space, then Office 2004 that needs 512 MB RAM and a 1.2 Ghz processor, you're done. IMHO, a minimum corporate PC should be a 1 Ghz P3 with 256 MB RAM. A more realistic one would be a 1.6 GB P4 (Or some kind of higher-end Athlon) with 512 MB DDR RAM. High end would be a full P4 2.2 w/ 512 MB RAM. Each "step" in this scale will give you about another year of functionality. Your P3 will be no more than 2 years, your P4 1.6 will be about three and your P4 2.2 might give you about four, depending on your apps.
Of course, if you're a company that has been happily running your DBASE III+ app on the 486's for years, this might be overkill. But if you're going to be using office apps, browsing, e-mail, etc. you're going to want the faster speeds and better performance, if not for today, but for tomorrow's apps.
This cost is sometimes hard to justify, but there's usually a fairly simple way around it. Ask your accountant what the depreciation schedule is on a PC. Most companies have a 3 to 4 -year depreciation cycle. It's not hard to show that spending $900 on a PC that's used for two years and paid for over four years isn't a good deal compared to a single $1500 PC that is used for and paid for over four years.
- G