Check whether appwiz.cpl is in your system32 folder (you may need, in folder
options, view tab: check the radio button show hidden files and folders,
uncheck hide extensions of known file type and uncheck hide protected
operating system files).
If it is not there, you may have a spare in C:\I386 or in
C:\Windows\servicepack files\I386 (If you have the latter it will contain the
latest version), or in C:\Windows\System32\DLLCache folder.
If so, copy it to your C:\Windows\System32 folder.
If it is there, you could check that it has not been disabled in the registry:
click start, run, type regedit, click OK. In the registry window that opens,
in the left pane click on the +es to expand the tree to navigate to
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies
Click the + next to that to expand its tree. If under that key there is one
called Uninstall, left click on it to show its contents in the right pane. If
there is a value called NoAddRemovePrograms set its data to 0 (right click on
it, click modify) or delete it.
Repeat for the key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies
Finally, if that does not work, try start, run, type sfc /scannow, click OK
[note space between c and /). System file checker will run and replace any
corrupt or missing files (may ask for your XP CD).
