Windows needs several different
kinds of system files in order to play nicely with the software that you're
running. If one or more files goes missing, the finely-balanced harmony goes
out the window. On top of that, the Windows itself may not work properly. Or it
might stop working all together.
DLL Files
The most important system files
are called DLLs. DLL stands for Dynamic Linking Library. They give
programs extra functions. When a program starts, Windows loads whatever DLLs
the program needs into memory. Over the years, Windows itself and many Windows
applications have become dependent on DLLs. So, don't delete any DLL file, no
matter how tempted you become. Doing this can damage Windows, one or more
programs, or both.
This isn't a hard and fast rule,
though. You can search for DLLs and if you find a duplicate, it's safe to get
rid of the older file(s). Or, you can delete the files that aren't in a folder
under c:windows. Before you delete a duplicated DLL, back it up. If an error
message stating that an particular application can't find the DLL appears when
you start it, just put the DLL back into the folder.
Driver Files
You also don't want to touch a driver files. These files
have extensions like .drv and .vxd, and enable Windows and Windows software to
talk to devices like printers, scanners, keyboards, and modems. Because drivers
translate instructions between your software and hardware, deleting a driver
file will cripple your PC's ability to communicate with the associated device.
Executables
Executables -- the files that
actually start an application -- have the extension .exe.
So, don't delete any .exe files. You can't start your applications without
them. It's especially important not to delete any of the executables in the
c:windows folder. When Windows starts up, it loads several programs into
memory. Without many of them, Windows will not function properly.
Another set of executables you
should never delete are those used to uninstall programs. You'll generally find
them in the Windows folder, and they have names like uninst.exe, remove.exe, or
unwise.exe. Some have cryptic names like unvise2qt.exe or st6unst.exe. These
files are used by the Windows Add/Remove Programs function to uninstall
programs. Without these executables, you won't be able to remove a particular
program when the time comes.