crazy display computer slows down

OS - XP service pack 2
1.8 g-herts Intel Cleron
512 MB memory
160 GB hard drive 110 Gb free space
Video Card - Nvidea geforce2 mx mx 400.
Mother - board asustek p4sdx

Computer has always worked fine.
Just upgraded the hard drive from an 80 G to 160 G.
the old 80 gig drive is now the slave drive.

Computer ran fine for two days after upgrading the harddrive.

After two days the display started acting weird as follows

A piece of the background would seem to attach itself to the mouse pointer and move with it.

A previous background would not go away when I opened up a new page. You would see some of the old background through the new page on the screen.

Thick lines of various colors would attach themselves to some object or icon on the screen.

The screen would seem to go to some low resolution "Picasso painting" appearance.

Print might look like jibberish.

At the same time other parts of the screen might look normal.

The computer would seem to slow down - sometimes youd click on something and nothing would ever happen.

Turn the computer off and things would go back to normal for a while and then start acting crazy again.

Things I have already tried.

Tested the CRT on another computer - OK
Did an XP boot repair. - OK
Updated the Mccafee anti-virus and did a full scan - OK

Still have the same problem.

What do you think is the problem?
Any suggestions?

 

maybe if you took off the background it might stop your problem

 

Bad video card? Video drivers?