ThRa...
If I understand you correctly, you want to scan you entire HD and do not want to change settings. Well, you don't have too!
Avast Home will always check ALL local drives .
Moving the slider from Standard to Thorough does not affect what drives are scanned, but how deep Avast scans into files....
like a sensitivity control.
Even if you did check Removable media, unless you have them attached, Avast will not read them, and bypass that mode.
Good luck,
techie101