I highly recommend a restore / reinstall of XP ... whatever is suitable for your PC as the manufacturers provide different options these days ... if it has a restore partition pressing F10 repeatedly on immediate boot should open it.
If it came with a restore disc use destructive recovery as your files are a risk now too
If it came with a reinstall disc use that.
Or if you have a full copy of XP use that.
What computer & model is it, and how old?