|Well you need the installation cd.|
Then as the means is somewhat lengthy ....but easy
google for doing a repair install.
Basically ...boot off cd... ignore first repair option use setup to copy files...then bail and select second repair option.
I have kept the above incomplete.......so google it and if possible print the 1.5 page of instructions out.
If you have the print out...you shouldn't miss a step and it will
replace any missing or corrupted file.
This is a level 1 of 10 in difficulty....very easy