OEM CDs are dangerous, it may be possible that this is a recovery CD which will wipe your whole disk and create one partition for Windows. The boot-loader will be overwritten for sure, but to repair that is rather simple.
But reinstalling would be pointless if the disk is dying. Take backups of your important data (hopefully you have backups anyway), then post the output of
Code:
smartctl -a /dev/sda
run as root.
