What is the application? If it is a software program for something like photo editing, that is probably something that the vendor supplied when the computer was built and has nothing to do with Windows.
If it is a Windows application, and you need to reinstall it, first check in Add-Remove Programs\Windows Setup to see if it's in the list anywhere for the various categories there, and if so, you normally can direct the installation (re-installation) to the Options/Cabs folder for what it needs. Use the Browse button at the start of the install to get to that folder.
It sounds as if it is the windows program that runs your whole control panel. If you can tell us what items won't show up in control panel....or if none of them will show up because control panel won't open at all, we might be able to help with that.
Now....If you have a cd burner device installed, you can use the burner program to burn a new installation disk for yourself by burning the whole Options/Cabs folder (or at the very least the CABS folder only). You are better off to get the whole thing if you can since there are other folders also included inside the Options folder that hold other programs and options that are useful.
Make sure you know where the setup.exe file for windows is located. If it is inside the Options folder, then open the Options folder in the burn program and burn only the contents, which will include various files as well as the subfolders....if it only inside the CABS folder, you will have to open that folder instead and burn the contents.
Some vendors only included the CABS folder inside the Options folder......and left out all of the extra folders. Some included everything in the Options folder, so what you burn will depend on what the vendor did.
Once you have that cd burned, you can get your Product Code Key through the registry. You can use the DOS command from the bootdisk as given before my post, or, if you can still get into windows, you can go to START, RUN, and type REGEDIT.
Now click the plus marks in front of the following folders.......
HKEY-LOCAL-MACHINE\SOFTWARE\MICROSOFT\WINDOWS
Now click the words CurrentVersion and you will on the right hand side items that you need to scroll through. Near the middle of the list will be the Product Code Key. It is a combination of letters and numbers that are 5 sets of 5 = 25 total so make sure you get them all.
TONI