did any of the later IBM machines have a full-ATX arrangement? I sort of liked the later all-black look.
Not sure on model numbers but certain late P4 NetVista towers (the ones with the backwards-leaning cases with flat fronts, whose front panels extend further than the top of the case) take what appear to be standard ATX mobos. PSU is a problem, it's fairly weird-shaped, but they actually have decent PSUs to begin with so if you're not building a monster you might be able to get away with it. 200-something watt output but they're decently reliable for OEM stuff.
Now I'm not sure, might be ThinkCentre towers.
This is the case style, anyway:
![](http://www.laptopenterprise.com/images//sku2019.jpg)
Thinking back on it, the PSU length is the problem. Standard units fit but interfere with the optical drive(s). Shorter drives may fix this, not sure. Don't quote me on this! It's been a while since I was in one of them.