|I suggest you download this malware scanner to scan your PC for malicious software and clean it. Before running the malware scanner, please do not forget to update its definitions.|
If no malware found, then you should check your PC for corrupt hdd and system files. Open a command prompt and execute the following commands. After the first command finishes, start the other:
CHKDSK /R /F
Note the blank spaces before the slashes.
Hope the above helps.