1. Defragment your hard drive regularly. If your hard disk is too fragmented -- files are too broken up -- Windows has to work harder to use and manage them. When it has to work too hard to read and use the files it needs, it will end up unable to run the basic user processes. Windows Explorer will be one of the first ones to stop working, so regular defragmentation of your hard drive will help a lot. If you have not defragmented it in a long time. the process can take a long time.
2. Reduce the number of programs running. If you have a lot of programs running simultaneously, it can use lots of memory (RAM). If your PC uses too much of its memory on running programs, it will not have enough left to run basic processes such as Explorer, and it will freeze or crash. Many programs run in the background without your knowing. Many of them are unnecessary; these are good ones to close. Press Control+Alt+Delete to see your task manager. Here you can see which applications and processes are running and end the ones that you do not need to run.
3. Reduce the number of programs that open at log-in. A common problem with Windows Vista and Windows 7 is that too many programs try to open when you start up your PC. This can use too much memory or cause so many programs to use the processor that it cannot handle them. At this point, a simple command such as opening a file or right clicking the desktop will cause Explorer to crash. To select which programs you want to open at startup, open your start menu, click 'Run' and type 'msconfig.' From the System Configuration menu that opens, select the Startup tab. From here you can choose which programs will open when you start your PC.
4. Use good anti-virus software. Windows Explorer errors can occur when a virus modifies or removes some of the files needed to run the computer properly. Removing these viruses will help reduce the impact they have on your PC's performance. After removing viruses, you might also have to run a registry-cleaning program. Registry files are often the ones that cause Explorer errors if you have viruses. A virus can remove or edit commands in the registry that are needed to run Explorer.
5. A last resort to fix Windows Explorer if it will not open at all and no other methods work is to reinstall your Windows operating system. This will erase all data on the hard drive, including all viruses or corrupt files that might have caused the Explorer errors, and install a fresh copy of Windows on your PC. Before doing this, be sure to back up all your important data.