If you have no System restore points, then you cannot use System Restore to reset you OS to an earlier date. Your options are:
1) Do nothing.
2) Change your System restore settings in Device Manager to allow it.
3) Do a repair install of your OS, which leaves your installed programs intact and usable, but would require you to download and re-install XP's security updates (available at MS' Windows update website.
4) Perform a clean install. You will have to have your product key and you will have to reinstall all the programs you want to use. Before you do this backup your data folders and files, including your Music, Pictures, etc. to another HDD or other media.