Problem with Snow Leopard update DVD

My 2009 Macbook Pro (OSX Version 10.5.8) desperately needs to be updated to Snow Leopard (and then Maverick). Problem is, I bought the mac in the US and now live in Europe, so I ordered the Snow Leopard update package from the German store – not realizing that it's a DVD rather than a CD.

I've read that my computer is supposed to ask what region I'd like to use when I insert a DVD. However, my computer just makes a weird, repetitive buzzing noise for a few seconds and then spits the DVD back out. Could this be a region issue? If so, how can I manually adjust the region setting?

 

Thanks for your feedback! Your point about software makes sense.

My drive will read a music CD, but it won't read the German DVD version of 'Shrek 2' (it's the only other DVD I have in the house).

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And yes, it is the €18 DVD that I bought online in the German iTunes store.

 

I'm reading on other forums that problems like this could be caused by a dirty lens that's simply not reading the discs properly. I guess I'll buy a lens cleaning disc tomorrow and see if that helps.