Question : Registry Restore

Attempting to get an application to work, I made some changes to the registry, and like an ID-10-T I didn't backup the registry first, now I've hosed up the system.  Currently any thing I try to open whether my computer, or command prompt, or by trying to call apps from the run command.  I get an error that says there is [...no program associated with this type of file, please choose which application to use from the folder options
I went to another system nearly identical to it and exported the registry, but the system won't let me import.  Not that the actual import is failing per se, as much as it is that I can't get to the file and attempts to call the registry editor or any program gives me that same [no application associated ...]
error.

Is there a way to merge this file with the system, or am I pretty much "up the creek" on this one?

Answer : Registry Restore

Restore your system to the last system restore point that XP took. This should restore your registry.

Start->Programs->Accessories->System Tools->System Restore.