I have it in XP and it works fine...and it didn't take so long to install.
Anybody installed CB Mega 2009 PlayerBase in Vista?

If you have a powerful antivirus which is is set to scan ALL files including archives (.cab, .zip, etc.), then it will take that long...

I do know that Vista SP1 and SP2 fixes SOME not all of the compatibility issues. If it does work, maybe it's just your computer. If it doesn't work, try getting the Service Packs.
Random Fact: VISTA stands for Virus Infected Spyware Trojan Adware
It took almost 2 hours to finish, something wrong with my disc or a Vista thing? I haven't found anybody else with this problem.