Pentium 4 3.06GHz
1 Gig Ram
40 Gig HD
256 MB AGP Video Card

Should I run Windows 7 32-bit or Windows XP?

Is there going to be a problem with using service pack 3 if I use XP?

I want to be able to run BobCAD-CAM as well.

It it was a poll I would vote for WinXP SP2. Serves me well.

Tweakie.

Buy a used box running XP Pro to run Mach3.  Clean that PC off so all it's running is Mach3 and dedicate it to the shop.  Run your CAD/CAM on the Win7 machine and network the two.  CAD/CAM consumes a lot of resources.  I wouldn't want that installed on the same machine running Mach3.  Even if you close the program, I'd worry about background processes that it may spawn and leave running.

I have mach running on XP and Win7 machines. Given the specs of the PC in question I would install XP. For Win7 you'll need more RAM and a larger HD.

If I were buying a new PC for Mach I would plan on using Windows 7. I just set up a little touch screen Shuttle with Win7-64bit (on a dual core Atom processor) and it works great.

CAD/CAM consumes a lot of resources.  I wouldn't want that installed on the same machine running Mach3.  Even if you close the program, I'd worry about background processes that it may spawn and leave running.

In general it is a good idea to have a dedicated machine for a CNC control. As long as your not trying to run your CAD/CAM program at the same time as Mach there is no danger of having them both on the same machine. Problems can arise sometimes even with simple things like Adobe Acrobat Reader wanting in install dial home programs that can really screw up your CNC control PC.

This will be dedicated to the machine. In fact the computer will be in the machine. I just want to be able to open and use BobCad if needed, not for it's main use. I will do my main CAD and CAM stuff on another computer.

The reason I ask about service pack 3 is because this computer does not work well unless I get all the updates. For some reason there is something it does not like about SP2, or rather it may be one of the updates you only get after loading SP3. Anyway, it works perfectly when all the updates are applied. 

So, if SP3 is a problem, maybe I better put a bigger hard drive in and rin windows 7?

I already own XP for this machine though, I would have to buy Win 7.

By the way, it would run BobCAD when it was 256Meg of ram, 2.4 gig celeron D, and using the onboard video. I am actually waiting for the parts to upgrade it to the specs I listed at the beginning. So, I don't anticipate there being any problem there. My main concern is a stable Mach 3.

There is no issue with SP3. I have a very, very old PC in the shop with a 1.3gHz processor, 512MB of RAM, etc and it happily runs XP-SP3. I have CamBam on it for the times I need to make a last minute tweak to something too. Other than CamBam and Mach3 I have installed nothing else on it.

For a stable Mach installation, start out with a clean install with the ACPI turned off. That takes care of the majority of issues.

Recent Dell box
XP SP3
No network connected: USB key works fine.
Runs very nicely.
Mind you, I stripped everything else off it - but Task Manager shows the system is mostly idling while running.

Cheers