You could try a systems file check to see if the issue is with the DLL itself. Open a command prompt (START > ALL PROGRAMS > ACCESSORIES > COMMAND PROMPT). Right click on the COMMAND PROMPT program and select RUN AS ADMINISTRATOR so you get full access.
In the box that opens type SFC / scannow and let it do it's thing. It may as for your Windows disc at some point to repair files.
For the record I have Win7-64bit and it runs OK.