So, you want to OC, but you have an OEM (prebuilt... aka, Dell, HP, etc) and have decided that you want to get a new mobo and get started. Before you jump into this, make sure you know these things.
Almost 99% of the time that you get a new mobo, you will need to reinstall your OS. This is because the new mobo will use different chipset drivers. Sometimes you can get lucky if your current mobo is the same chipset as the new one (or close enough) but that rarely happens. So get ready for a completely new install and everything that is involved with that, and be pleasantly surprised if it does work out.
This leads us to the next thing that you MUST know before you do this. If you have an OEM copy of Windows Vista (aka, you don't have the disk, and it came pre-installed on your computer) then when you install the new mobo, you likely will not be able to use the same product key again. This is because the Product Key is registered in conjunction with the BIOS. Microsoft has determined that a new mobo = new computer, so you'll have to get a new Product Key, otherwise you might not be able to install your OS again. OEM copies of windows come with a one time use license key
This is confirmed with Vista, most likely with Win 7, through apparently XP and earlier are not effected by this.
Don't let this scare you away if this is what you really want to do, as neither of those things are hard to do. Its just a nasty surprise when you can't use your product key, and now that means you need to spend another $100 on an OS that you already had.
On the other hand, once you have transplanted your first CPU into your new mobo... you'll be well onto your way to being a full system builder, and will probably never buy a pre built again. You'll be able to build better performing computers for less money, and will have learned a valuable skill.
I have just seen this happen a few to many times, and wanted to make this information more readily accessible to those that need it. Hopefully this helps someone out.
Note: This was written to be part of the Phenom II Overclocking guide