What types of utility programs did you install?
Do you have a Windows XP Installation CD? If you do, you should try to Repair the Installation 1st.
Go into the bios and set the CDRom as the 1st Boot Device (if you don't have a XP CD then the setup may be on a separate partition of your Hard Drive, maybe D: ?)
Save and Exit from the bios, PC should restart
Follow the on-screen instructions as they appear. You'll get a screen asking if you want to repair your system using the recovery consule. Skip This. That is not the repair we want. Continue on, a screen should soon appear telling you something like this.
Setup has found an existing version of Windows installed. Would you like to continue with the installation. It should have the option to Continue - or - Repair the existing installation
Select - Repair the existing installation
Sit back and correctly answer all the options given