I was thinking on buying a used HP Vectra VL400 P2717T computer. Does anybody know if the parts in this computer will fix into the newer cases that are out there. What issues could I run into. Please help if you can.
True, but since mATX boards will fit into ATX cases, if you're going to make the jump, go to a full ATX case.
I don't know if it's a problem, but it's not uncommon to see pre-builts with a non-standard PSU. I would check on that as well to see if you ned to factor that in to your upgrade cost.
With HP business-class, even the budget ones, I believe they still use standard PSUs. In fact, I think they typically use unmodified Gigabyte motherboards.