I've built several computers for my family from scratch without problems but not done too many major upgrades of same.  I decided to upgrade the motherboard/cpu in my own computer, replacing the Chaintech MB (with Athalon XP2500) I built it with originally (less than 2 years ago) with a Chaintech 7NJL6 (and Athalon XP2900).  I had hoped that the MBs were similar enough that my system wouldn't balk at restarting, and I would just install all the new MB drivers after I RESTARTED.  No luck.

Now I can't get Windows XP to boot up at all.  I get as far as the window asking me how I want to start the system (Safe mode, debugging, LAST Known Configuration that worked, etc).  All selections lead to either a restart or else the screen GOES totally blank and never comes back UNLESS I do a hard restart.  I can enter the BIOS, and have confirmed a reasonable boot device order (Floppy->HDD 0 ->CD).  When I turn on Posts and then restart, the upper right of screen flashes many post NUMBERS, not ending consistently on any one post number in particular.  I've pulled/switched memory chips, unplugged all unnecessary peripherals.... I figure I must have violated some basic rule of MB upgrading, out of ignorance.

I had a similar problem a few months ago when I replaced an (apparently) bad Verto video with a different one (also Verto): I eventually had to reinstall Windows XP, getting approval for Windows re-registration over the phone.  I'd hate to do the re-install again.  I never made a start-up boot CD for this computer, though I have another in the house (Kid's computer) with XP running, though on a Shuttle Celeron MB.

I use this computer mostly for home video-->DVD editing and conversion, as well as the usual home stuff. The current equipment is:

450 W power supply
1 GB ram (2 x 512)
HP DVD drive
HP DVD burner
Chaintech 7NJL6 MB
Athalon XP 2900

Sorry for the long post, this is my first.  I 've searched the Microsoft site and many forums, haven't found a solution yet.  Any help appreciated.

-Brian
How to Perform a Windows XP Repair Install