XP Freezes at Logon, Shutdown

I've got a baaaad feeling that I'm just plain hosed here...

Old processor died (XP 1800+), replaced it and the mobo. When I log on to XP, the machine hangs as soon as my desktop appears, and must be restarted by the switch. It occassionally hangs just before the logon screen pops up (black screen and mouse cursor). When I enter safe mode, things are great until I try to shut down, at which point the machine hangs, and will not save any changes.

I tried to enable boot logging, but it hangs, and I can't read the log file. I tried to chkdsk /f, but safe mode/command prompt has the same shutdown issue.

I tried to overlay install through safe mode unsuccessfully, also tried to install by booting from the CD to no avail (this gets me a string of seemingly random BSOD's...bad_pool_caller, blahblahblah_in_non_paged_area, you_have_a_bad_haircut_and_nobody_likes_you, etc). I've also said 4 dozen Hail Mary's, 1.5 dozen Our Father's, completed 2 Hopi Rain Dances, and run around my block naked 3 times with no better result.

Spec's:

AMD XP2200+
GA-7DX+ (don't ask....)
Promise ATA133 Card
40GB WD
Phillips 16X DVD
Lite-On 48X CDR/RW
512MB PC2100 RAM
Chaintech GeForce2 64MB
300W Antech PS

Shall I just scrap this crap and start over? Please say it ain't so!!!

You mentioned an inplace install through safe mode... what do you mean?

The usual way is to boot with the xp cd and when it gets to the point of asking you which partition you want to put xp on, you choose the repair existing install option...

Once I got into safemode, I popped the CD in, ran setup, and it prompted me for type of install. I selected the inplace option, gave it my product key, and it began copying files. When it went to shut down, it hung (as is it's habit), and I can't get the install to complete. I tried doing it by booting from the cd, but that's when the BSOD's started. I don't even get to the point where I can choose repair.

So what bsods have you had? Specifically need the message and the first set of numbers from the stop error please..

before I scrapped it(read format and start over) I would try installing a fresh copy of xp on a new hard drive in this box just to rule out a bad motherboard or chip.
One other thought, maybe the power supply is the problem. I was pricing supplies yesterday and noticed a number of 350 watt models labeled AMD approved to XP2100. I had a similar problem with win2k where the pc worked fine in win98 but froze after logon in win2k. A beefier power supply fixed it.