I had a machine brought in last week where the attemtped installation of NOD32 had failed because the previous AV package had not uninstalled properly. Easy, thinks I, but wonders why anyone would want to replace Kaspersky Internet Security 2009 with anything else as it is rated one of the best by the trade. A residual problem relates to IE refusing to open some web pages, especially those with a password entry on them.
On looking at the machine after I had run the downloadable Kaspersky removal tool (http://support.kaspersky.com/faq/?qid=208279463) this then cleared the errors but on doing a further check I found the remains of a McAfee suite in there. How Kaspersky allowed this I don't know but I suspect that the reason Kaspersky failed to do the biz properly was because of this.
Anyway, I used a McAfee removal tool ( go here for instructions and a link to the tool http://service.mcafee.com/FAQDocument.aspx?id=TS100507 ) which at first found nothing but I am glad I looked at the manual as it explained that you may have to run the tool from the command line or run box.
Once that was done the system came up clear.
Moral of the tale - Kaspersky is innocent!

From the above link