First, it's illegal to use cracks and such to bypass the security of software which you don't have legal access to. The rearm command however is legal.
Install Vista (or Windows 7) without a serial.
Use it till the timer hits zero days, or close enough to zero.
Open up a command window by going to the start menu and typing in "cmd" then hitting enter.
In the command window type "slmgr.vbs ?rearm" or "slmgr /rearm" which will reset the countdown until the install expires. You can do this up to three times. This will give you up to 120 days of active time without a serial. After that, you'll need a valid serial (which I luckily have).
If updates are similar to Vista you should be able to install any and all updates while under the 30 day grace period.