I have an iMac5,1. I'm wanting to know if I am able to upgrade it to OS 10.6?

Yes. Read the original question too fast.

Allan

Yes. All Intel Macs which came with 10.5.8 or earlier can run Snow Leopard.

Allan: 6 is not 8 and Snow Leopard is not Mountain Lion. Furthermore, the actual iMac requirement for running Mountain Lion is 7,1, not 5,2.

(69670)

Fill it up with RAM. Your system supports 3GB. Crucial or OWC are reputable, respected vendors.

Yes, Snow Leopard runs great on my ealier 4,1.

Plus you would do better with a matching (2x2) 4GB kit from OWC for $60 even thought your 5,1 will only access a little over 3GB.

See > Understanding Intel Mac RAM - Mac Guides

And > iMac (Late 2006): Memory Specifications which also states that you can install 2GB modules in both slots.