Win XP: How to clean boot

Note You must be logged on as an administrator or a member of the Administrators group to follow these steps. If your computer is connected to a network, network policy settings may also prevent you from follow these steps.
1. Click Start, click Run, type msconfig in the Open box, and then click OK.
2. On the General tab, click Selective Startup, and then clear the Process System.ini File, Process WIn.ini File, and Load Startup Items check boxes. You cannot clear the Use Original Boot.ini check box.
3. On the Services tab, select the Hide All Microsoft Services check box, and then click Disable All.
4. Click OK, and then click Restart to restart your computer.
5. After Windows starts, determine whether the symptoms still occur.

Note Look closely at the General tab to make sure that the check boxes that you cleared are still cleared. Continue to step 6 if none of the check boxes are selected. If the Load System Services check box is the only disabled check box, your computer is not clean-booted. If additional check boxes are disabled and the issue is not resolved, you may require help from the manufacturer of the program that places a check mark back in Msconfig.
If none of the check boxes are selected, and the issue is not resolved, you may have to repeat steps 1 through 5, but you may also have to clear the Load System Services check box on the General tab. This temporarily disables Microsoft services (such as, Networking, Plug and Play, Event Logging, and Error Reporting) and permanently deletes all restore points for the System Restore utility. Do not do this if you want to retain your restore points for System Restore or if you must use a Microsoft service to test the issue.
6. Click Start, click Run, type msconfig in the Open box, and then click OK.
7. On the General tab, select the Process System.ini File check box, click OK, and then click Restart to restart the computer. If the issue continues, the issue is with an entry in your System.ini file. If the issue does not continue, repeat this step for the Process Win.ini File, Load Startup Items, and Load System Services check boxes until the issue occurs. After the issue occurs, the last item that you selected is the item where the issue is occurring.

How to start the Windows Installer service
Note The Windows Installer service does not start if you disable Load System Services. To use Windows Installer in this case, you must start the service manually:
1. Click Start, right-click My Computer, and then click Manage.
2. In the left pane, click Services and Applications, and then click Services.
3. In the right pane, right-click Windows Installer, and then click Start.
If you run a Setup program without manually starting the Windows Installer, you may receive the following error message:
The Windows Installer service could not be accessed. Contact your support personnel to verify that the windows Installer service is properly registered.

How to return from a clean boot state
1. Click Start, click Run, type msconfig in the Open box, and then click OK.
2. On the General tab, click Normal Startup - load all device drivers and services.
3. Click OK, and then click Restart when you are prompted to restart your computer.