ok this is what you do if you dont want any lag.
first of all I strongle sugest that you get rid of Norton. trust me I had it, and all it does is lag up you computer.
Make shure you dont have any adware, or spyware on your computer. That will lag up your comp badly too. Get something like Spybot:
http://www.download.com/Spybot-Searc...-10401314.html
Uselly I use Spy Sweeper or NoAdware
Make shure you dont have any firewall. You dont need it.
Now go to Start-Run-write in "msconfig". Click on Startup and get rid of anything that you dont need to run in the background.
Defragment your comp, and clear up more space for you computer.
These are just some basic things you need to do if you dont want your computer to lag.
Now if its still lagging, then I would suggest rebooting your comp or getting it fixed.