No virus protection? OK. That may be a bad idea.
it's probably not the hard drive
You most likely have a virus in there.
You can take out the drive, install the drive as a second drive in a working XP computer, recover your files, make a backup of your personal files.
You can then do a repair install (without reformatting the drive) or a new install of XP, using an XP disk. Try a repair install first.
Did your computer come with an XP disk?
Did your computer come with drivers on a CD?
If not you will need to buy an XP disk (XP Pro SP3 if you can get it) Try amazon or trinity software, it's cheaper.
Hope you save your personal files as above.
Unfortunately, since you did not have an anti virus installed, there's very few options, other than what's above.
There is one more possibility, although it does not always work. Buy Norton 360 or Panda internet security 2010 on a CD, put the disk in the drive and start the computer.
The CD will scan the drive and possibly neutralize the virus. Then you can try the recovery options again, or use the computer again. Anyhow, once you get it going, be sure to run anti virus from now on.