I have done a search but couldn't find anything relevant.

for the last few months I have had AVG Antivirus (free version) installed on my PC as I had been having compatibility problems between Avast and my Comodo Firewall. When it was first installed it would tell me it had checked approx 250,000 files/items every morning after finishing it's daily scheduled check. This was a similar amount to Avast. The last 2-3 weeks however it will check between 80-109,000 files. I opened up the box marked "Scan Selected Areas" and found that the only box ticked was the one at the bottom saying "Other Settings" and a sub box was ticked here saying"Scan System Areas before the test starts". Just as a test I put a tick in all the boxes on this screen and did a test. Result of this selected areas scan was that AVG checked 271,560 files as opposed to the 89,937 files checked on this mornings Complete test Scheduled scan.

I'm not sure why AVG doesn't check the complete PC as it did before and possibly this is how it is supposed to operate but can anyone point me to a tutorial or such like for AVG Antivirus similar to the one found on this site for Avast.

If you want everything scanned, then click on "Scan Computer" at the top; if you want only one drive, or selected folders scanned, then click on "Scan Selected Areas." Using the latter, you can select (or deselect) folders to scan by opening the appropriate drive.
For example, I have two drives on my computer. I do not scan, normally, the D: drive, since this contains data transfered from my C: drive and thus already scanned. I use "selected areas" to skip the D: drive and thus save time.
Regards,
John