Windows 7 is a differnt beasty and to register a dll (writting 32bit DLL to 64 Windows7), follow these step:
1) Place the DLL in the c:\windows\sysWOW64 folder
2) Go to accessories and Command Prompt and run cmd "Run as administrator".
3) From command prompt write the full pathway to register a dll,
For example: c:\windows\sysWOW64\Regsvr32.exe c:\windows\sysWOW64\gif89.dll
Explanation of Regsvr32 usage and error messages refer to MS KB 249873
