AV 2011 had quite a lot of bad press initially so I'm not sure that I'd trust it for a while.
If a rootkit is present, it's inadvisable to run AV/malware scans from within the affected OS as the system could well be hooked before the anti malware software is initialised, thereby rendering it unreliable at best.
With this in mind, it's worth having one of the many Bart's PE type releases such as UBCD4Win
which contain updateable versions of SAS, MBAM and Avira etc and the Kaspersky Rescue Disk 10
ready to hand.
These are images of bootable CD's which should be burned on a known clean machine and used to boot the affected machine. Both have very wide ranging network adapter and TCP/IP etc support which allow anti malware etc software to be fully updated before use. The UBCD type boot media utilise "MiniXP", DOS and often Linux type interfaces with many useful and powerful applications included whilst the Kaspersky media is exclusively Ubuntu based. The Kaspersky media contains wide support for WLAN adapters.
Be aware that many of the Bart PE type images may contain "pirated" software.
Edited by Deadbeat (Fri 04-Feb-11 00:00:43)