Alot of people don't quite understand that PC control has changed alot since the past good of days of softare running ON windows...DOS was a simple and great working platform, but is now ignored by most sadly.
Most GOOD products utilize a microkernal of some type to ensure their machine control Real time operating system runs independantly from a client system, like good 'ol winblows. This is nothing new, Old school kids like me know about thinks like machine virtualization, IBM has been doing it for a long, long time on things like mainframes, running hundreds of vm instances as all independant 'machines' running on one big peice of mainframe iron. The advantages of doing so are huge.
Why also did microsoft snap up Connetix recently, after their VirtualPC product. VMware and others have shown VM'ing is great even now on PC hardware.
What i'm trying to say here is that many of the products out there will run a micro kernal on the system, which in turn will host two child kernals, one being windows and one being their machine control RTOS. SO windows crashing and being the peice of **** it *can* be bares little direct harm on PC based control. Windows can crash, and the main kernal and RTOS keep on chugg'n.
Of course alternatives like Linux and other Unix's and RTOS like QNX provide a much more stable base, and in many of those examples above are very low cost, or no cost. This is why the embeded market is hot over linux and open source. These will creep into all forms of control idustry. I'm doing my part >
Another thing to keep in mind is that x86 pc hardware bases do keep very stable in their spec and design. Embeded 486 and now pentium systems are still widely used. A simple PC104 base system with compact flash memory and some I/O serve tasks very well, and have been around for a long, long time. You don't NEED full fleged pc's. And remember kids, if you write portable code under something as fluid as linux, well you can port to any platform easily
Don't associate microsofts pathetic products and performances as the benchmark for general computing devices used in industrial control applications.
Remember Microsoft is not the reality the rest of the non-windows worshipping world knows. There is a promised land, but its not redmond washington
Entirely clear from your minds Microsoft and all your experiences with them. Only then will you being to see think and understand your choices more clearly. Of course, to do so you've got to drop windows. Its nice on the linux / mac side now (both unix boys).