|Do you have any other USB devices connected? If so, remove them and try booting again. If that is no go, then try booting without the keyboard and mouse connected. If the computer then boots into Windows then connect the keyboard and mouse, one by one while the computer is running. Watch the screens to verify the device has been installed.|
Are you using the on board graphics or do you have an add in graphics card?
To verify this issue is NOT a co-incidental hardware issue I suggest you use a different computer to download a live version of Linux. There are many. Live versions of Linux run from the media you place them on and don't require installation. This can tell you if there is a hardware problem or if it strictly Windows related.
You can also use Linux to backup you personal data.
Linux puppy is small and easy to use.
If still no go, then you may need to perform a factory restore. That will cause you to lose all personal information and any added programs and device drivers. You will also need to update WinXP.
To learn how to perform a factory restore see page 54 of your linked manual below.
I suspect the replacement motherboard may be different from the original one.
Do you have any backup media or a factory restore disk set?
One other thing that I just thought of that might help. Boot into the BIOS (setup) again and disable all non-essential integrated hardware. Network card, parallel port, things like that.
Page 50 of the manual explains Dell Diagnostics. That might be worth while running.