Can't install XP ... or 98se ... or 2000 ... or ...

The boot order already is floppy-cd-hdd. Both set in bios and manually selected at startup.

I've tried 2 HDD's in my system. same thing happens. I've tried my HDD in a different system, and it works, which leads me to believe it's a motherboard error (already removed graphics, ethernet etc. to ensure it's not a hardware issue with them).

I've also upgraded the BIOs, found no change so downgraded it and also reset the CMOS.

Also changed the CD drive to ensure it wasn't that, but that made no difference either.

These are in addition to those stated in my original post.

IF you did, the major hurdle that you have is that the MBR is still setup for Windows 7. It isn't compatible with XP. Running bootsect with a /nt52 parameter will set the MBR for XP, so that you can install XP. Having said that, you have had a few Operating Systems on this drive, that have left their rubbish behind. A Format won't remove the rubbish, that is why I suggested to use DBAN. Or killdisk as OH Smeg has suggested (must try to remember that). It really does, give the drive, a new lease on life.

But if you want to try it another way that will leave the rubbish:

Boot from your W7 DVD and on the first screen click Next, click Repair your computer, click Next and select Command Prompt.

Type in bootsect.exe /nt52 ALL /force

Type exit

Restart the System and swap the DVD for the XP CD. Your Operating System will have to make room for the rubbish that was left on there.

There is a third alternative that I would consider a lot better than running the bootsect command and that is to use DiskPart. Not as good as DBAN or KillDisk but preferable.

I like to work in multiples of 4096 so multiply that by 6 or 8 and you have a Primary Partition of 24576 or 32768 depending on what you intend to install on the Primary Partition. The smaller Partition the better as the read and write heads don't have to travel so far.

This is an example using DiskPart with a hard drive, assuming that you are working on a single drive. You would be at the recovery console:

using DiskPart. For example, from a command prompt, type in these commands and press Enter after each one.

diskpart
select disk 0
clean
create partition primary size=32768
active

Meanings:

diskpart = runs the DiskPart program.
select disk 0 = selects the first Hard drive. If you are working on a second hard drive it would become disk 1.
clean = erases the drive.
create partition primary size=32768 = only use this if you want more than one Partition. You can create more Partitions using Disk Manager. Otherwise it is just
create partition primary
active = marks the Primary Partition as the Active Partition, this in turn makes the drive Bootable.

A Description of the Diskpart Command-Line Utility

http://support.microsoft.com/kb/300415

Keep us posted. :D

Edit: clarify a point