Software install hung Win2k, now boot probs

OK, supposed to meet w/ boss today (though technically now yesterday) immediately after lunch. She was gone when I got back, not to return for 2+ hrs. Since what I need to do the rest of the day/week hinges on what she heard in an earlier mtg, I thought I'd dork around for a couple hours until she got back.

Rockstar Games is having a little promotion, which includes a free dl of the original GTA, so I figure "Why not?" I dl the file, save it to hdd, reboot (since I'd earlier been working w/ some resource-hungry progs) and then attempt to install GTA.

About 1/2way thru, the install hangs. I wait, I wait, I go to the bathroom, it's still hung, I run a couple errands to other depts, it's still hung. Desktop is all blue (background=none in Win2k), all icons are invisible, so it's just one big desktop.

Another couple minutes, no better, so Ctrl+Alt+Del. Can't remember exactly what it did (onscreen) at this point, because a few seconds later, PC speaker makes the "flatline" sound (steady tone).

No keyboard combos affecting anything, so I attempt the restart button on the tower. No effect. So, I use the Power button on the tower. PC finally powers down. I wait about five minutes. With trepidation, I hit power again. Doesn't get very far into the boot/POST when it just stops.

Black screen. White underscore cursor in the top left, flashing. No keyboard combos do anything here, either. Waited five minutes, no change. Turned off, then back on again. Same old black screen w/ white underscore cursor.......

PC is running Win2kPro, 256MB RAM, 1.2GHz Celeron, 8GB/30GB 5600rpm hdd.

Any thoughts? I'm not the type to run to IT, I usually troubleshoot at least a few of their prelim steps for myself and anyone in my dept before calling/involving them. I also would rather not call w/out trying anything on my own first when the issue was likely caused by my installation of unapproved 3rd-party software.

Primarily because of the 2nd sentence in the above paragraph, I've got a few friends in IT and could pull a few favors if I had to, but would rather not put them in that position if it could at all be avoided. Any assistance/advice would be greatly appreciated!

Oh, and - The End. Sorry, I know it's long. It's late and I'm rambling........