new day computer 1 me 0

I have a gateway computer with xp professional which has been working fine and this morning it says operating system not installed. I'm not very knowledgeable when it comes to this so please reply as a beginner.

 

Basically it's either not detecting your hard drive at all, or your data is messed up to the point where it doesn't recognize XP (or any other operating system) as being installed on the hard drive.

Do you know how to get into the BIOS to check if it's detecting the hard drive? Follow the link below if you need a little help.

http://computernotions.com/html/bios_setup.html

If the BIOS detects it, then it would appear your XP install is corrupted. You can boot from your XP install CD & run set-up...see if it detects your current XP installation. If it does, you are given the option of repairing the existing installation, or doing a complete new install of XP. If it doesn't give the repair option, you'll pretty much have to do a new install to get things working again. Here's a site with some more info on the repair install process:

http://www.michaelstevenstech.com/XPrepairinstall.htm