System restore doesn’t work properly

I used WinXP Home SP2. Recently I tried to divert WinXP Home SP2 to WinXP Pro SP2. I upgraded the system successfully.
When the upgrade is successfully done I clicked on my computer to go to system properties but I failed to find system restore tab. After that I went to system restore service but found this problem.
Could not start the SR Service on Local Computer. Error 5:
Access is denied.
Now what can I do? Need your help friends.
