How can I upgrade the OS on my 5 year old MacBook Pro 17. It is currently running 10.4 (Tiger). I have an IMac 27 running Lion but have Snow leopard discs which came with the purchase. Can these be used to upgrade?
If they are the grey discs which came with the iMac, then they will be machine specific and will not work on the MBP anyway. You will need to purchase a retail copy of Snow Leopard from the Apple Store for about $29 and upgrade from that. I presume your MBP is Intel and not G4.
First off, you need a 64-bit processor to install Lion "on top" of Snow Leopard. Secondly, Snow Leopard is still available at retails stores and Apple Stores.