OEM or Retail

I am looking at getting W7 for another one of my computers. I have never really had to buy my software before because my sister in law worked for Microsoft and I got it for free. She has since went on to another job and I don't get those benefits anymore. So I now am faced with buying W7. Should I buy OEM or retail. I know OEM is cheaper but what happens when something goes bad and you have to put in a new part. How is MS about dealing with this?

[caperjack]

I'll say Buy Retail ,I may be wrong but, not sure what difference it would make ,but why buy oem ,oem is a disk used by original eqiptment maunfactor[computer maker ] ,so thye can customize it to add all kinds of junk[trial versions of useless software ] and driver specific to there computer ,
as for changing parts I have done that many time and at best all I had to do was re-activate windows by phoning MS

[scudzilla]

Technically, OEMs are not for sale. Only bundled with new hardware. However, many stores ignore this condition. Microsoft doesn't seem to care as well. If you can find a store selling OEM, go for it. It's much cheaper than retail. It's key is locked to your mobo, but you can contact Microsoft if you need to transfer it to a different system due to failed major hardware (I have yet to experience this though). You won't be getting the free technical support with it, but with google, daniweb and other resources via internet, you won't need it anyway :)