strange uncontinuos black stripes in upper and lower part on screen & desktop icons

I have an IMAC G5 17"
since 2 weeks happeared some strange black uncontinuos stripes as showed in pictures
anyone knows what happened and how to solve it
they started to happear next day my brother downloaded a work document from e-mail and print it on my imac
it was a .dot document.....don't know if problem is related with that

Have you repaired permissions and rebooted?

i made it now
it fuond 80 wrong permissions i repaired it but nothing changed

Which OS X version are you using? You might want to try downloading the latest combo updater from Apple for that version and installing it to see if it resolves the problem.

Apple - Support - Downloads

i have mac os X 10.4.11
i tried with mac updater and it says no update available
i have changed HD recently and in Apple center they put that version

Download it directly and run it, it won't display in Software Update:

Intel:
Mac OS X 10.4.11 Combo Update (Intel)

PPC:
Mac OS X 10.4.11 Combo Update (PPC)

i made also that but unfortunately nothing changed
if i open word (office 2008) those lines appear on all screen but if i open other applications including excell i see them clearly.....
it could be something related with that?
how i unistall it.....just put it in trash as usual?

opss i forgot many thanks for your help hope we can solve it at last LOL

There's an uninstall included with the Office 2008 application. You can use that, and then reinstall Office to see if that helps.

i have unistalled but nothing clanged grrrrr