Can you tell us what model your machine is and do you have any disks for it?
Can you put Disk 1 into the drive then Restart your computer and when the first screen comes up tap the F10 key till you see the boot menu.
When it opens cna you select to boot the CDRom drive first and a menu will open so you can select system restore
Just choose that option and follow the prompts and it will tell you when to switch the disks and when to remove them.
Let me know if you have any issues
Glad to hear that got it for you,
Just print out the steps I posted and keep it safe in case you need it again in the future.
More than welecome,
If we can be of help in the future just let us know