I think some clarification might help here - there are OEM disks provided by manufacturers with computers at point of sale - albeit a rarity - and there are OEM disks builders can buy cheaply.
I've tried using both in the past and particularly with the first category, have come across serious driver issues - unresolvable because the system fails to start with the drivers the CD provided. I've even known it to fall over when, say, a Dell disk was used on a different Dell system. As the OP would have been lucky to get a CD with an OEM machine when he bought it, it's safe to assume he's bought a disk separately so needs to be certain it doesn't come bundled with drivers.
Bought Windows 7 OEM separately, I built my own computer.
I installed W7 yesterday and today decided I needed to start again (I made a mess with some system files), so wanted to know if I could reinstall.
I was able to clean install windows on my HDD without any problems, thanks for the help guys.