i need help!! whats going on?

My mac has a problem. I use firefox as a browser and everytime i try to download something like skype it downloads it to my desktop. Then when finished i go to click on it and the icon does the opening motion (the zoom into the face) but does not actually open. I think it bounces on the bottom bar once. and then NOTHING HAPPENS. so they will download but they will not launch.

What have i done for this to happen. Someone recommended that i update my java so i downloaded that but i doubt it worked as i have this problem of not being able to open things which download. I am using a g4 laptop ibook think.

Do you think my computer is old and knackered and i just need a new one? Everything else works fine though.

Any suggestions would be very helpful as i know nothing about this.

Thank you thank you xxxxx

Does it do the same thing when you download with other browsers?

yes it happens with internet explorer and opera. I don't know if this is related but when i try to upload photos to facebook the browser 'unexpectedly quits' . this happens with every browser.

thanks for replying!

NOTE: Thread moved to appropriate forum. Not just anything goes in Anything Goes