Where did you d/load it from? If you paid for and d/led it from the official site, then there isn't any password. You'll need to have admin priviledges to install programs on your account.
There are many scam sites out there. Have a read through these threads:
Membership? - **WARNING ** BEWARE** - Download p2p Clients ONLY Thru Official get your $$$ BACK!!!(music members)
If you d/led it from somewhere else without paying for it, then your on your own. Hope the file's not infected
.