Though Vista SP1 makes your system much more faster, stable, reliable and also add a whole host of new features too. But if due to any reason(personal preferences too) you want to uninstall SP1 and if you are doubtful regarding some questions. Then I have the uninstall procedure jotted down as an FAQ for you.
Well, How can I get rid of SP1 for good?
It's simple as ever. Goto control panel, click "Programs," then, in the next window under "Programs and Features," click "Uninstall a program."
Make sure to Click "View installed updates", then select "Service Pack for Microsoft Windows (KB936330)," and click "Uninstall."
How long does it take to uninstall SP1?
In normal circumstances it will take 20 to 30 minutes to uninstall the service pack. Similar to the installation procedure of SP1, the uninstall is a three-stage process. There is one reboot in the middle, then another nearer the end. If the middle restart doesn't happen automatically, however, so you have to stick around to click a button. The rest is hands-off :) .
Are there any SP1 bits left on the machine?
No, but the updates that Microsoft required prior to offering SP1 through Windows Update - dubbed "prerequisites" by Microsoft - will surely remain.
These include the January KB935509 update to BitLocker, and two others originally delivered in February - KB937287 and KB938371. As you may recall, the middle update of trio, KB937287, was reported that it had sent many users PCs into a death spiral of endless reboots. Microsoft yanked the update several days later from the automatic delivery list; users were still required to download and install it last week, however, before they were able to "see" SP1 on Windows Update.
Are there any other Microsoft-approved ways to uninstall SP1?
According to the KB948537 support document, the company says users can also roll back to a pre-SP1 state by using Vista's System Restore feature - but I really can't assure you if things go fine this route.
Microsoft spells out two options: one "offline" -- to be used if the PC isn't connected to the Internet or can't connect, perhaps because of SP1 -- and another dubbed "online." The former requires that you have your original Vista install DVD and a PC that will boot from the optical drive.