My PC is a laptop Acer 6930G
3Gb Ram - 250 GB Hard drive
Windows Vista Home Premium SP2
Attached 3TB of USB Hard disks - HP Printer - Mouse
Netgear Wireless Router wireless connection.
The system is sometimes so slow during full virus scan that, for example, on loading Windows mail it shows 'not responding' - until it does.
Apart from full updates I have now run 'disk maintenance' and deleted its suggested data. I had 832 Mb of temporary files and prior to tidy up I only had 8Gb of free space on a 120 GB C drive. Data swaps due to 'hard faults' were frequent and I had a 6GB cache.
The computer at risk message showed. Turned on protection and it said protected. But after a few seconds the at risk message appeared again. I repeated actions about six times until the secure message stayed on.
Since reducing active programs and open web pages, disk tidy up etc the event has not recurred. I also had a number of blue screens and now believe that the problem was system congestion causing time-outs in the various waits in the programmes. Maybe - scanning a large file with hits coming in for open web pages and mail caused the at risk message..
I assume you have 2011 version ie the 1 with about on top right of opening screen. If so you can exclude files and folders you know are safe from custom and scheduled scans so scans can be faster. I exclude all the windows 7 backup zip files and avi folders.