I fail to see what this has to do with VB.NET, but... To unregister the .DLL, if it has such a capability, try supplying the full path to the .DLL to REGSVR32:
regsvr32 /u "C:\documents and settings\someone\somepath\dllname.dll"
If it comes back and says that the "DLLUnregisterServer entry point was not found", then you could just delete the file. RageInTheMachine9532 "...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome