Jennifer,
In order to get the best advice, you will most likely need to define what you mean by upgrade. I doubt you will be able to upgrade your processor much on a six year old motherboard. You will probably be able to add RAM, but even that will be difficult. As someone said, if you go with WIN7, you will need at least 2GB of RAM and maybe even four.
It sounds like if you are talking about updating hard drives, processors and RAM in six year old machines, you would do better just getting new PCs. They would come with the latest processors, DDR2 memory, etc. If you wanted to use 64-bit OSs, you would need a 64-bit processor. Most RAM now is DDR2 or higher, and I doubt would be compatible with your computers. So, other than adding compatible RAM and maybe a faster hard drive, I am not sure how much more efficient and fast they will be.
I love XP Pro and, to date, has been the most stable OS Windows has made by far. But, you can't dodge WIN7 for too much longer, and it is more compatible with software than Vista ever was. If you were going with new PCs, then I would go ahead and take the WIN7 plunge. But, if you already have XP Pro, then I would stay with them. Why purchase WIN7 and then get it free on a new system. And, IF you do get WIN7, get WIN7 Business or Ultimate (just my opinion).
8GBs of RAM in a 64-bit WIN7 system is sweet, but I would probably take the extra 4GBs in each and put them in the server which is running the SQL servers and everything else.
Refurbished is OK. I am a new type of guy, but that's just I. It's sad that as doctors we have to watch our dollars.
