I am having an old Pentium III 600 Mhz and i do not experience lower system performance if I put the Avast scanner on high instead off normal,… in fact all systems run at “high”,…

Pc configuration:

Pentium III 600 Mhz
640 MB ram (maybe this explains why i “feel” no difference)
20 GB harddrive
Windows 2000 Pro SP4