My PC (running XP pro) keeps looping the STARTUP. When I turn it on, it will get to the Windows logo screen, then go to continuing setup screen (I tried reinstalling windows) then stop and reboot itself over and over. I tired installing new memory and no luck. Any suggestions on what to do next?Can you post more specs about your computer. Things like amount of RAM, type of video card, processor speed. Things like that. With the info you've supplied us with I would have to LEAN towards a failing stick of RAM. Are there any beeps? However without more information about your system I'm limited on what I can help you with.when you install back,did you agree to the (EULA),if not,that coulb be one of the reason.otherwise,its a hardware issue It sounds like you may be having a hardware failure – especially since you formatted and still get errors. You should try another hard drive and hard drive controller if possible to rule out any issues in that area. Also, have you installed anything else recently? Something as seemingly-benign as a program or SOUND card can cause strange BEHAVIOR such as this.You say it "go to continuing setup screen". So I assume that Windows never finished installing but got stuck at some point? When it exactly does it reboot?
Did the computer also reboot before you tried to reinstall XP? If so when?

And post more info on your system like the previous posters suggest. Have you added or removed any hardware LATELY? (Besides the new RAM)