Aren't you having fun, presumably you're pressing delete to get into the BIOS set up? If that's so and the virus has accessed the bios and set a password to enter the bios you may have real problems. Switching the M/C off and removing the bios battery may or may not remove the set password, consult your mother board manual for a possible answer.
Do you have an old hard drive anywhere that you could plug in instead of the existing one? If so unplug the current one and insert the old one and power up, if it says operating system not found then insert the XP disc if you have one, or borrow one (you don't need to register the install immediately) and see if you can install it, if you can then plug the other drive in as a slave and you should be able to operate on its file system and remove the virus manually.