I have seen this before.
- Re-boot your computer, and while the computer is in POST (power on self test) invoke the BIOS setup by pressing F2, F10, or DELETE on your keyboard (depends on whose BIOS it is).
- Look around for the advanced processor options until you find the option for 'Execute Disable Bit'. Turn this feature OFF.
- Save changes in BIOS and restart the computer into Windows.
- In Windows, go to the Control Panel, and invoke Automatic Updates. Turn this feature ON.
Leave the computer running for a few hours until it downloads and installs some of the updates on its own. The manual update method won't work until it gets some critical updates, but after it does the manual method will work.
You have until April 8 2014 to have all the updates installed. After this date your patched Windows XP will have no more support from Microsoft.
It sounds as if you set up your computer to launch a single user profile. Don't blame the staff at Frye's for blowing away the whole OS, because in your situation that is really the only option they had. If you have some crummy desktop computer on your network, save everything precious on both computers in the future for redundancy.