Is this a Dell PC desk top and is XP updated to service pack 3? The reason I'm asking is because about 5 or 6 years ago Dell used a build in small security program in XP for it's laptop units that also inadvertently got carried over to some of the desk top pc's. One of the nasty side effects of the security program on the desk top models is it prevented some programs from loading and running. I know because it happened to my Dell 8400 running XP Pro. Not with Mach 3 but with another program. Apparently it causes the run.exe to hang during the loading process because of a system registry error. The bad news is its not a software fixable problem... its a BIOS bug problem. At the time Dell would replace the motherboard however that option is long gone now. The problem effects random software but not all software for some unknown reason. I spend several weeks digging into this issue. Due to the age of the old Dell I gave up and moved everything to a new Windows 7 platform. I'm using the Dell 8400 for Mach 3 only now.