Vlk
2
Does the continual running of the on access scanners in avast 4 use a lot of memory- i only have 64 meg ram.
It uses about 12MB of virtual memory (not necessarily physical memory).
If you’re running Windows 9x, 64MB will be fine. If 2K/XP you should consider buying more memory - it’s cheap!
Would it cause the pc to freeze.
We hope not! 
Is it best to have the on access scanner running all the time for the virus protection to be most effective??
Well, yes, for most users it’s best to leave it running all the time… Otherwise you’d always forget to turn it on when needed. - And you know, bad luck always strikes when you expect it the least… 
Vlk