[citation][nom]A Bad Day[/nom]Windows' DEP isn't perfect, I've seen legit programs (HL2.exe, Adobe, etc), sometime MS's own software, get targeted and terminated. That includes very recently installed computers with no internet connection.[/citation]Then something is wrong with your hardware, or yourself. If you have these sorts of problems on clean installs with no internet, you're doing something seriously wrong and should probably stick to Macs as you've implied. The odd badly written program might cause this, but that can happen on any system and is usually fixed quickly with a patch if said company wants to stay alive.
[citation][nom]A Bad Day[/nom]As for the IT department, I'm fairly sure there are companies that neglected their computers and networks. There was one horror article from Popular Mechanics about a company whose IT stuff was hell.
Overheating server rooms, constant network lockups, emails that take several minutes to be sent, unable to use internet-connected phones, etc..[/citation]Again, hire new IT people because the ones that let their networks get like that are idiots, and this has nothing to do with PCs, hardware or software.