SPMBT/SP2WW2 anyone?

[Imp]

Turning UAC off reduces your systems security though.

The increased security risk is minimal & can infact be negated easily.
Use a virus checker or firewall that has a sandbox & leave it on.
Less intrusive than UAC as only asks you the first time something new tries to do something, so when you install something or run it for the first time & does not move files.
TIP turn off the sandbox when you install a safe application or occasionally you can end up clicking a dozen times or so though normally it recognises its an installer & just asks you once if it should ignore it.

If your a security freak you should not be using an administrative account for day to day use. That is far more secure than UAC but a pain as need to switch accounts to make any changes to your system.