If you're on a 64 bit operating system, the REGASM might have created registry entries for a 64 bit app. You'll need to modify the registry file to relocate the entries to the branch used for 32 bit apps.
The assembly has to go into the GAC until you use the codebase argument to make put it in a specific location on the hard drive. Or, you could use manifest file rather than the registry and have it as a local assembly.
I'd suggest starting off with the GAC, and then progress to the other options only once you get the GAC approach working. One step at a time....