Typically documents and such are rarely infected. Its usually system files and such. Considering the problems you're experiencing it could be difficult to remove things. But malwarebytes is a good tool, there are some rootkit removal tools as well.
To attempt safebackup of your stuff, run a linux boot cd and copy your important stuff to a usb stick or usb hdd (i wouldnt recommend a network share). Avast antivirus can scan the stick/drive before booting up windows. so install that, then have it scan the drive before booting the OS.