instaall XP on aa Dell

Hi,
I have been asked for help in reinstalling windows xp on a friends comp.
It is a Dell about six years old and came with XP the system is full of viruses and spyware but not much user stuff - pics etc - so i adv her to copy the pics to a usb disc which has but when she tries to install xp she gets an error that says she needs to upgrade the BIOS as it is to old to take XP but she already has XP on it?
She has tried the recovery partition and a copy of XP but it says the same thing
I won't be able to get down til the beginning of december so I can't get the full system specs but I do know it has a 20gb hdd 512mb mem and a 750ish processor.
Does anyone have any general info on what to get her to try til I go down as I haave never come across this before.

[MovedGoalPosts]

Best option to try is to make sure that boot from CD is enabled in the BIOS. Make sure the Windows XP Install CD is in the drive, reboot, and make sure the CD is accepted at the prompt. From there I'd go for the new install of windows option, Delete the current partion (s), which forces a reformat when you create the new partion.

This will however remove all of the recovery partition stuff, so it's an all or nothing option.

With Dell it should be possible to go to their website, input the Dell service tag, and that iwll allow download of various drivers, BIOS updates and stuff that might be available to suit XP.