System slow down while scanning ??

i installed avast 4.8 with no problems…i removed previous antivirus properly .i use windows xp SP3.and i have AMD sempron 2.0 Ghz processor with 2 GB RAM …The problem is when I’m scanning big compressed files system slows down badly.it makes it very hard to browse web pages while scanning…i never faced this problem in any other antivirus software…and i tried every antivirus out there…so ,is it normal in Avast??..or something is wrong ???
and if i might add, the internet protection is great in avast this antivirus might be the one after all…(i use windows defender and superantispyware free on the side)…

When you start the scanning, avast will think you want to run it, of course, then the priority is to run the scanning. You can right click the interface and sent it to background to have your other program/services running at more priority.

Then this slow down is normal in avast!..i thought there is something wrong…maybe they will fix this problem in the next version. thanks for replying.

I won’t call it a problem… it’s like it is…
Compared to other antivirus, avast has a good (fast) on-access resident scanning but has (never) the speediest on-demand scanning for sure…

Welcome to avast forums.

Thank You Tech…I’m really satisfied with Avast to this point…nice On-access scanners…and the best of all is this forum…MAN there is alot of info here ! …u guys r truly evangelists ! ;D
keep up the good stuff .