Currently Being ModeratedOct 12, 2012 2:05 AM (in response to Porkyy)
Remove any items in System Preferences > Security > Login Items
Same for HD > Library > Startup Items
Then restart your Mac.
but as soon as I try to open an application, I get the rainbow wheel.
If there weren't any apps listed to launch when you startup your Mac, the startup disk may need repairing.
Follow the instructions here.
I see you posted in the Snow Leopard v10.6 forum but it helps to tell us exaclty which OS X installed. Troubleshooting suggestions may depend on that information.