At startup, folder with finder folder and a questionmark?

i have an i book G4 that my dad gave me like 3 years ago. Because i was new to mac i messed up....jajaja

i was whatching some videos on youtube or so! and a pop up came on and said that there was a posible troyan or virus threat. so i desided to download an antivirus for mac.....avira, from download.com i think. and i started to clean it.....it said that there was alot packages that didnt belong to any folder so i dicided to throu them into the trash. i turned the computer of and later when i turned it on again it wouldnt go passed the white screen with the apple loading! i gave up on it and send it with this guy that was gonna fix it. but when i got it back i turned it on and there was a grey screen with the finder folder and quicky turned to a questionmark repidetly! it does not accept the leopard disk i have......its cloned cuz when i got it it didnt come with anything but the charger cable!

i also tryed with an unbuntu recovery disc and a fedora....

i dont know what to do!!! please help me MAC EXPERTS!!!!!

I GAVE UP!