Mac OS 10.5.8 multiple issues all the sudden, info missing?

I'm a fairly new Mac user, and couple of days ago, wed 25th, switching from one profile to next - we have 4 on our mac, there were certain things missing from each one.

one profile missing mail, firefox, and safari, one profile missing all but safari. so under one that safari was working had to re-install firefox, and got back online under each profile there. Mail is not on any profiles, and iphoto was not on any profiles until just a moment ago when i did a software update and iphoto came back and back on all profiles. Even system preferences is gone and does not show in finder on profiles, but shows on dock on one profile but as question mark.

has anyone seen this before and know what would cause it?

when things went screwy voice command was turned on accidently, and figured out how to turn that off, so possible the apple key and another key was hit during this time to make things go screwy? Please help.

thanks.

Does each profile have its own Applications folder, or are all using the one in the main Hard Drive "directory"? (not sure if that's the correct term, maybe it should be "window" or "path")