I sold a bunch of older Dells that ran Mach3 just fine including one to a friend that still uses it to this day to run Mach3.
P4 2.0ghz and 512 ram.

Don't sell a cheap computer short. As you have probably read, it is the driver test that needs to run well and weather it is a Dell or a white box it really nakes no difference.

If you are running an external motion controller then pretty much any computer that meets the minimum specs will work.

I have several small form factor compaqs that will not pass the driver test but run my dspmc without any trouble.

Mike

I had some installation trouble, but my router is now running Mach3 on W7 on an older computer.  You really need to make sure that the DVD you get is a 32 bit version; the normal retail or OEM DVD you find around is 64 bit.  While you can run Mach on 512MB, W7 is a pig with that little memory, although 1G seems to be enough.

Newegg does have a 32 bit version OEM 1 pack for $99 with free shipping.

Did you ask the shop if they could sell you a licensed version of XP with the machine?  They may be able to do that for less than $100.

Did you ask the shop if they could sell you a licensed version of XP with the machine?  They may be able to do that for less than $100.

The little Dell that I purchased locally has XP Pro on it with the legal activation code for XP Pro, that all came with the upgraded memory to 512mb and a seperate half-height 32mb video card, 1.8ghz Pentium-4 and a 20gb HD.  All this with a 90 warranty for $150.
I am also very happy to report that I have successfully driver-tested this little computer and then I hooked it up to the control box and everything worked like a champ.  Very happy with my purchase so far, so unless this really takes a dump I will not need W7 at this time.
Thank you all for your time,
Tom