OK, since you mentioned sysdm.cpl, I'm guessing you already checked in System 32 folder.
U can try and run a chkdsk, sfc /scannow from run,cmd or, you can try to replace it with a backed up copy from your own Windows.
So, if the scans don't work try this:
System files almost always have backups somewhere.
This has one (I checked on my XP) in Dll Cache folder in System 32.
But to view Dll Cache folder, u need to make sure that Show All Filed And Folders are checked and the Hide Protecting Operating system files is unchecked in Folder options.
Then, go to C:\Windows and do a search, or go directlly to DllCache and locate sysdm.cpl.
Copy it and place it in the System 32 folder and try to open it.
Let me know if it worked.
And just in case I would do a Malwarebytes scan on your PC.