Upgrading from Windows XP32bit to Windows 764Bit, What are some things I should be aware of?

In about 2 weeks, my new computer will arrive and I will be giving this computer to my brother. The following are the specs on the computer I am currently on:

AMD Phenom X4 9600 Black Edition - Quad Core Proc - 2300MHz/core 4 GB of DDR2 ram ATI AMD radeon HD 4870 Video card with 1g onboard Ram X-FI Creative Fatality Soundblaster Soundcard Killer m1 Nic

I figured I would throw another 4gb of ram into (albeit DDR2) and Windows 7, as the XP32bit I am presently using and low ram amount is horrible. If he finds use with it and wants to get more out of it, then I would help him upgrade the Video Card to something more powerful with AMD.

Thoughts?

I've never made the transition of operating systems. Fortunately, i don't have many programs at the moment to worry about AND I have an external HD that is 1tb, so everything is backed up. I figure I could order from newegg and get both items for around $200.