when you say freezes .... permanently .... or just for a few seconds or so?
AVG will certainly check the files ... but which flavour of ZA?
you should only have 1 virus checker running
are you using NTFS or fat(32?)
NTFS likes 20%+ free to work comfortably ...
fat requires less ... 20 or so MB is more than enough
UNLESS it's your system drive ....
windows will create a pagefile 1.5 - 2 x your total RAMsize .... (size will vary depending on ram ... and what you are doing at the time
so you need to figure that into the "free" space also
512 mb ram = 1.5 - 2Gb + 20% of 60Gb = 12Gb
= 13.5 Gb Ideally ..... you have 7.8Gb
not ideal
If you can afford ... get an external USB or NAS drive
shift as much as you can to that