Black Screen after Windows XP Starting....

Hi, did you ever get an answer to this problem as my flat mate is having a similar sounding one.

His PC was working fine earlier this morning:

Athlon XP 1700+
Abit KX7-333
512mb DDR
Windows XP Home
20GB HD

until he put in another 20GB HD this afternoon.

As soon as the hard drive was in the problems started.

I think that when the hard drive was first put in, he set the jumper on his hard drive wrong.

There are 4 places the jumper can go. Master, Slave, Cable Select and one that on the HD itself is just called 'Jumper'.
It was put on the 'Jumper' setting and rebooted.

After initially not working at all, the jumper was put to the 'master' setting.

Now the post screen starts complaining about CMOS checksum error, press f1 to continue, hit F1 and it says the system is checking devices (apparently it always does this, i assume its his mobo). Then the screen goes into standby mode.

Take out the second hard drive and put everything back exactly the way it was. No luck there, different message (CPU Software wrong or something), go into the bios and its been reset. Change it all back to what it was, reboot and the screen goes blank.

Tried moving the jumper to Cable select, same problem, the screen goes blank. Tried a compeltely different HD (with windows installed), same problem. Tried a different GFX card, same problem.

Reset the bios to 'Fail-Safe settings', same problem.

Tried inserting the windows XP cd to see if it could boot off that, same problem, screen just turns off.

Does anyone have any idea what could be the problem with the computer?

Thanks a lot.

Vizz