By far this is the only tool for windows Vista, I found which claims to re enable the registry editing (Regedit), Cmd / Taskmgr / System restore Config / Folder options config and Run command. It claims to re activate regedit , without messing around with scripts or third party registry editors. The publisher mentions that "It is coded in .net but doesn't need .net installed because .net dependencies are included in the program making it fully portable"
Link to Re Enable Portable download
If you are looking for instructions for windows XP, please click on this link.