Do you have an installation disk for your OS? If so, you can run the Windows Repair feature, which will not delete any of your files or settings...only Windows Updates in XP. This repair feature will repair any damaged Windows files. If you can post your OS, a link to help with the installation will be easy to provide...
Here is an excerpt from a post on another site I found about your particular issue...
"This is caused by the virtual memory page file being set at zero. Also some people say having external drives and a new device installed can also cause this problem. If you increase the voltage to your ram then this sometimes can also trigger a new response. Heres a little more info from a forum I've looked at, some of which may or not be useful. Hope this helps.
Partmgr.sys controls the Page File, which, if the PF's become corrupted, will prevent Windows from working (even loading in some cases)."
