I have is Compaq desktop PC it is set up that you have to have a password to login it I got it at a yard sale and they didn't tell me that , what can I do

How do I do the full system restore windows xp

Go back to the people that you got it from at the yard sale and ask what the password is so you can use it... or ask for your money back.

To do a restore, you probably need the disc from Compaq.

Go to HP's site and look for instructions on booting to the restore partition for that model.