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I have a computer with Vista and no CD.

If I wanted to uninstall and reinstall SP2, but safely, i'd like to be able to roll back.

If it can be done safely, how would one go about it?

And is it possible to do it wrongly, i.e. like not being able to roll "back"(to any previous state, like when it was installed, or just after it was uninstalled).

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2 Answers 2

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It is generally a very safe operation, but if it fails, it will do a very good job of rolling it back to where you started all by itself.

Once a service pack is installed, if you decide to uninstall it, you would just do that in "Programs and Features", the way you would uninstall any update.

That said, to guarantee successfully (un)install, Microsoft has developed the "System Update Readiness Tool". If you want to improve your odds that it will install without error, run this tool. It can take anywhere from 15 minutes to 2 or more hours to complete, but it will fix underlying problems that you will never find on your own.

http://support.microsoft.com/kb/947821

As always, to be sure, you should have an image of the computer.

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It has saved me in the past, and here is another one I suggested this to: superuser.com/questions/300517/… –  KCotreau Aug 1 '11 at 22:41
    
By the way, why would you want to uninstall it? Maybe there is a better way to accomplish what you want. –  KCotreau Aug 1 '11 at 23:01
    
Well, at the moment I have no need to but in future I might, it's because if a file or files become missing or corrupt, and they were needed, and I can't find the OS disc, or because vista is sp2 and the disc isn't streamlined sp2, then uninstalling and reinstalling sp2 might help. i haven't tried it before but it's just a thought. though if it were just a few files i could download them from the web. if it were more or I couldn't find them on the web then maybe that option of uninstalling and reinstalling sp2 might be a good one? –  barlop Aug 1 '11 at 23:39
1  
In that case, the right choice is then to run "sfc /scannow". That is EXACTLY what that is for. When you install the OS, and later update it, critical files, including for the service packs, are stored and a database with hash tables to ensure that they have not been changed. It may ask you for a disk for original files, but I am not sure if that is the case with Vista and later since I think those are also stored on the drive now. msdn.microsoft.com/en-us/library/aa382541(v=vs.85).aspx –  KCotreau Aug 1 '11 at 23:53
    
I tried it on a vista machine once and the msg I got back that time was "Windows resource protection found corrupt files but was unable to fix some of them. Details are included in the CBS.log" In that situation it was only one file where the log said corrupt or "cannot repair", and the file wasn't important. But it couldn't restore the file. If it was important/needed by windows, then i'd have wanted to restore it/them. –  barlop Aug 2 '11 at 0:47

It is safest to do a clean boot of the system, un-install and re-install while clean booted.

To Boot Clean in Windows 7 and Vista

Accessing the System Configuration Utility

Click Start type msconfig in the search box and press Enter

Configure Selective Startup options

  1. On the General tab, choose Selective Startup
  2. Uncheck Load Startup Items
  3. Select the Services tab
  4. Check Hide all Microsoft services
  5. Click Disable all
  6. Click on OK
  7. Click Restart.

After performing the necessary steps, restore your system to a normal boot by doing the following:

  1. Click Start type msconfig in the search box and press Enter
  2. On the General tab, choose Normal Startup
  3. Click Ok
  4. Click Yes, when asked to restart your computer

.

To Boot Clean in Windows XP

  1. Click Start --> Run --> Type MSCONFIG --> Click OK
  2. On the General tab, choose Selective Startup
  3. Uncheck Process SYSTEM.INI file
  4. Uncheck Process WIN.INI file
  5. Uncheck Load Startup Items
  6. Click on the Services tab
  7. At the bottom, check Hide All Microsoft Services
  8. Uncheck all boxes in the window or click the button labeled Disable All
  9. Click OK
  10. Click Restart

After performing the necessary steps, restore your XP system to normal boot by doing the following:

  1. Click Start --> Run --> Type MSCONFIG--> Click OK
  2. On the General tab, choose Normal Startup
  3. Click OK
  4. Click YES, when asked to restart your computer
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would you do the equivalent disablings in xp's msconfig? –  barlop Aug 2 '11 at 1:08
    
Check my edit above –  Moab Aug 2 '11 at 2:06

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