Hmmm well, if you're feeling lucky ... from the start menu, go to the 'run' command enter 'regedit' then navigate down the tree on the left to ... hkey_current_user - software - microsoft - internet explorer - main you should see quite a lot of stuff on the right, including RunonceComplete RunOnceHasShown both of these have values of 1 when the 'runonce' has finished
I think you have to turn off your firewall/security/ad & pop-up blocker temporarily to allow the runonce script to run (then turn the security back on, of course!). Stupid Microsoft.
I've been running ie7 on 4 pcs for about 8-10 weeks and the only problems I've had are with norton 2007 crashing it on one machine until norton released a fix early last week. We have about 20 engineers here, and the majority stick with ie as it does the job and i.t. support it About half have upgraded to ie7 so far.
btw if you add the runonce values - make sure they are DWORD !