[q=rubah]is it a crt or an lcd monitor? (a box or flat)[/q]

The picture's rolling, so it's probably a CRT. LCDs tend to display a jumbled but static picture if they're dying. If it were an LCD, it would probably require the panel to be cracked to get the picture described.

If it is a CRT, it could be a number of things. The best case would probably be a monitor sync problem, in which case you could fix it by going to Control Panel > Display > Settings > Advanced > Monitor and changing the refresh rate. I doubt it's that however, since I would expect it to affect the whole screen.

It could feasibly be caused by a magnetic field close to your monitor. If a CRT sits in a magnetic field, the field will deflect the beam of electrons, so that the phosphor in an area of your screen is never illuminated.

The worst case would be that your graphics card or monitor (probably monitor) is at the end of its life, and this is probably the case. How old is the monitor? As it ages, the motor driving the magnets around the electron gun will weaken and eventually fail, which means no more screen. It can be fixed, but is relatively expensive, so you'd be better off with a new monitor.

I recommend that you try another monitor if you can get your hands on one and see if you're still experiencing the same issues.