I tried all those registry cleaners that say they are free, and then to fix the problem it cost. I've restored my computer twice. once in safe mode once not. I can't access a lot of stuff like my security center and other important components. In the system32 folder in my C: drive rundll32.exe is there but it doesn't look the same as the one in my D: drive system 32. How can I get it back.
Please help thanks in advance.

First, we can go on for days telling you why registry cleaners are no good and that they can damage your system. But here's a link that explains it: http://www.windowsbbs.com/showthread.php?t=61015

How have you restored your computer? Have you used System Restore or some other process/procedure?
What are the properties of Rundll32.exe in your C:\Windows\System32 directory - and what are the properties of the one in the D:\WIndows\System32 directory? (it's not unusual for them to be different - but the one in C: should be the same as or newer than the one in D:)

Hello usasma,

thank you for helping. I used system restore, I don't have a disk my computer came with vista on it. The runddl32.exe in the C: drive System32, it's properties are empty under the details/general tab. It just has the size and the date modified. The one in the D: drive System32 has the file description-Windows host process and all the other information like: type, file, version, product name, product version, copyright, and so on. all of that is there and it just looks legit compared to the the other one. When I try to open my security center it pops open the black CMD box for like a second and then closes. No error message just that.

Most times it's not rundll32.exe that's the problem, but rather it's an infected DLL file using the rundll32.exe process to launch itself.
You can submit the questionable rundll32.exe to http://virusscan.jotti.org to see if it is infected.

Also, here's a link with a bunch of free, online scans that you can try. There's instructions on what to do at the bottom of it: http://www.bleepingcomputer.com/blogs/usas...?showentry=1252