1. Click on 'Start' and go to 'Run' in Windows XP or click in the Search box in Windows Vista and 7.In the Run or Search box, type 'Msconfig' without the quotes. You are going to use this utility to tell the operating system to start up in 'Safe mode' Why? Safe mode only loads necessary operating system files. When files are loaded into the operating system, they can be harder and more complicated to fix.To set your computer to boot into safe mode. Click on the 'Boot.ini' tab in Windows XP, or simply the 'Boot' tab in Vista or 7. Select the 'SafeBoot' and 'Networking' options and press 'Apply.' You will be prompted to reboot. Click OK. Upon reboot, your computer will be running only the necessary services to complete this process. You will still have Internet capability. After reboot, go to step 2.
2. Open the command prompt by clicking on 'Start,' then 'All programs' and open the 'Accessories' folder. Right-click on the 'Command Prompt' icon. On the right-click menu, select 'Run as Administrator.' A black box will appear on your screen.

3. Type in the command prompt: SFC /scannow and press 'Enter.' This command initializes Windows System File Checker. The file checker will begin scanning all the system files, including .dlls. Once it finds an error, it will replace the broken file with a new one.It's worth mentioning that in using this utility, you have the option of scanning just one particular file. However, it is wise to scan all protected files to ensure that there are not multiple issues.
4. Monitor the command prompt window. In some, but not all cases, you may be prompted to insert your Windows install CD in order to complete the repair. If this happens to you, simply insert the CD into your drive and press the 'Retry' button.
5. Close the command prompt once the file checker has finished. You now need to set your computer to boot back up normally. Go back to the 'Msconfig' utility and uncheck the 'SafeBoot' and 'Networking' options. After that, you are safe to reboot your computer, and your dll libraries should be free of errors.