ya nothing bad will happen to the computer if you use all your ram it'll start using the hard drive which will make the computer really slow, but it won't blow up or anything
download a program such as freeRAM XP pro and that tells you how much is free and how much is used. If you want to slow down the computer then run norton or mcafee anrivirus with as much bloatware as you can find. That should slow it down a pretty good amount.
yeah , what do you do with your computer , ifyou are only using internet etc than they are good specs , maybe add more ram and it will be better , and does your dad know a lot about computers