It would be good to know more about how your system became afflicted because if you did not apply a restrictive policy yourself, somebody or something did it for you.
However here is the brute force method to reset/clear any policies that may have been applied to your system if those polices have been applied by Group Policy Editor or Local Security Policy. If a policy has been applied some other way, from a Microsoft
Fixit, a direct registry edit, malicious software, etc. this method will not work.
The information on policies are stored in two folders on your system (assuming Windows is installed on your C drive):
c:\windows\system32\GroupPolicy
c:\windows\system32\GroupPolicyUsers
Navigate to the c:\windows\system32 folder and rename the folders to something that you can remember - maybe with a .bak extension:

Then click the Start orb, All Programs, Accessories, right click Command Prompt, Run as administrator and respond with an administrator password if prompted:

Then from the Command Prompt window enter the following command to make Windows aware of the changes:
gpupdate /force

Then enter 'exit' to close the Command Prompt window and see how your system behaves now.
Restart your system to be sure the changes "stick".
When you are satisfied your system is working properly you can delete the renamed folders from before.