My imac cant regconise the finder after upgrading the itunes7!!!!!!

Question

after restart, the computer seems to run slower, only the top right icon shows up but the others run slowly. also there's no icons (all the folders & files) on my desktop!!!!!!! when i click the tool bar's finder icon, it doesn't work!!!! only safari survives!!!!
what's wrong with my imac????? is it the itunes issue or the hardware problem (something crashing?)
please help!!!

Answer 1

"Is it run under disk ultility?"
Yes.
"so what should i do after doing that?"
Restart. See below.
Save and/or quit your applications & doucuments
Go to Applications>Utilities Folder
Click Disk Utility
Click the Volumn (HD) that you want to check.
Click the Repair Disk Permissions button. (Don't worry about verifying)
When the repairs have finished, you will see the “most important thing”:
Permission Repairs Complete
The previliges have been repaired or completed on the selected volumn.
Restart your computer.
See Knowlege Base Article http://docs.info.apple.com/article.html?artnum=106214 Using Disk Utility and fsck to resolve startup issues or perform disk maintenance
It is recommened that you should Repair Permissions:
After installing and/or updating an OS
After installing software
===================
Regarding the "Norton AntiVirus Error", apparently you need to update your Anti Virus program and/or should have disabled it when updating iTunes if the downloading instructions stated so.
If you still receive the error after repairing permissions, you will need to run LiveUpdate to update Nortons per their procedures.