laggy on good comp, but doesnt lag at all on rubbish laptop

How often do you clean your pc? Disk clean-up and defragments? if you dont do them often you should get into the habit of doing so that could be a cause of it. I know a site with 2 very good programs used for doing disk clean-ups and disk defragments. I will link them here.

http://www.piriform.com/ccleaner thats the downoad link for the disk cleaner.
http://www.piriform.com/defraggler is the program to defrag your pc.

You should always do a disk clean-up with Ccleaner atleast once a day and use Defraggler to defrag you're pc atleast twice a month