Well you could definitely use them to erase and reinstall windows, but as far as REPAIR goes, that would depend on the manufacturer. I believe with HP/Compaq you can but I'm not sure about the others.
However, you can enter repair mode without disks on Vista/Win 7 machines by hitting F8 several times after the manufacturer/BIOS screen disappears. After doing so, select Repair Your Computer from the list that is rendered. This will give you basic recovery options including startup repair, system restore and a command prompt. Many manufacturers allow you to reimage back to factory defaults from this screen as well, without the need for disks.
These options will likely not help you with update problems or other weird glitches. You would either need to do a clean install or have a retail copy of Vista/7 (which ever you have installed) which you can use to do an 'upgrade' on top of your existing install which keeps user data and reinstalls the OS (which would likely fix windows corruption, driver issues, etc..).