pop your windows disc in the cd drive and click start the click run and type sfc /scannow
to set your paging file in: control panel/system/advanced/performance/settings/advanced/virtual memory/change and click custom size.
set the min and max values to around one and a half to two times your installed ram,ie/set both to 512 if you have 256 ram or there abouts.
after typing in the values click set and ok.
you may need to restart the computer.