I'm not a pro but I have built one computer, so I'm not a total newbie, either.
I'm currently nursing along a vintage 2003 IBM ThinkCentre -- old enough to be IBM branded, but it's Lenovo hardware. I did a significant upgrade back in 2007 and was impressed with how easy it was to open up and get access.
I'm thinking of reusing the case for a new PC. I'd expect to take out the old motherboard (RAM, CPU, etc.), power supply and hard drive and put in new equivalents. The optical drives are in good shape, and I'd expect to keep them.
Is there any reason why I shouldn't consider doing this? Have I missed anything that should be obvious?
Thanks for your input.