After much research, I found a particularly nice forum post on the Dell site. The procedure works if it involves the Vundo-based Winfixer (WinAntiSpyware, WinAntiVirus, Blackworm, Amaena), which can be identified in your HJT log in the O2-BHO section, if you find any of the following names:

MSEvents Object
ATLDistrib Object
MFCOptimizeClass Object
ADOUsefulNet Object
WTLHelper Object
RawExecAction [...]