I would start by checking the add-ins it's trying to load. File, Options, Add-ins. You could disable them all temporarily and see if the load time improves. The put back the ones you need one at a time.
Do you have the installation media/files? I'd suggest a removal and fresh install of 2010. Upgrading software can introduce bugs, in my opinion. You could also create a new profile on the PC, and configure Outlook with your email account (out of interest; what are you using? POP/Exchange?), and then see if it loads any quicker.
@Jim - thanks. Removed Exchange add on (not needed) and load time is now "only" 2 mins, it was 4-5. Still slower than 2007 but bearable.
@Mark - loath to do this, but if I do will it retain all my settings - presumably pst file is retained intact?
@Malcolm - thanks but I start up on inbox.
@Jon - Office 2010 folder is 14 not 12. If I go to that file outlook.exe it just loads Outlook, sorry don't follow your solution.