Massive problems because of this. Data Execution Prevention shuts it down and although I have selected DEP to allow it to run it still won't. Often followed by a "can't reference memory at..." Registry problem? Hardware?

With the problem program added to the list, it should run unless it is chaining other exes or dlls that are causing the DEP memory trigger.

Have a look here (http://support.microsoft.com/kb/875352/en-ulk) particularly about a third down the page under "System-wide configuration of DEP" where you can switch off both software and hardware DEP from the boot.ini file.

Good Luck!