How can I tell what changes are made to the registry?

Start the registry editor (regedit.exe)

Select the key you want to monitor

From the Registry menu select "Export registry file"

Enter a file name (notice if you want to export the whole registry just select the "Export Range All") and click OK

Perform the change (install some software or change a system parameter)

Rerun steps 1 to 4 using a different file name

Run the two files through a comparison utility (for example windiff.exe)

If you are using windiff, select Compare Files from the File menu and you will then be prompted to select the 2 files to compare.

Once compared a summary will be displayed stating if there are differences, to view the changes double click on the message

Press F8 to view the next change (or select next change from the view menu)

You have now found what changed!