This is what I have.
AMD Athlon 64x2 Dual core processor 4200+
2.20 GHz 2 GB of ram
Will windows 7 64 bit be OK to use? Will CS3 and PortraitProfessional 8 work with it?
Spec wise, you're perfectly fine. Having 2GB of ram is good. What you need to worry about is if drivers are available for your add-ons. Most likely your motherboard/nic etc will have drivers built into 7 but for peripherals, etc. you'll have to check for those yourself since I don't know what you have.
It's fine, but a bit unnecessary to run an x64 OS on a system with only 2GB. I would suggest adding 2GB more of RAM. You'll be able to fully utilize all 4GB and should notice a significant boost in system performance.