If someone is working in a work/office inviorment it isn't quite as simple as just getting rid of windows xp. Doing so while not having everything migrated and working correctly can cause huge problems.
The easiest way to tell you how to fix this is from these quick and easy instructions from online
Insert the Windows XP bootable CD into the computer
When prompted to press any key to boot from the CD, press any key.
Once in the Windows XP setup menu press the "R" key to repair Windows.
Log into your Windows installation by pressing the "1" key and pressing enter.
You will then be prompted for your administrator password, enter that password.
Copy the below two files to the root directory of the primary hard drive. In the example below we are copying these files from the CD-ROM drive letter, which in this case is "e." This letter may be different on your computer.
copy e:\i386\ntldr c:\
copy e:\i386\ntdetect.com c:\
Once both of these files have been successfully copied, remove the CD from the computer and reboot.
That is a guide that I have had saved on my computer for a while, I remember it now just easier to copy and paste.