Why are uninstalled programs still there?

I recently accidentally uninstalled my AVG antivirus software. A friend advised me to just use system restore to get it back - and it did. My question is: what is happening to all these programs that you uninstall, are they all still lurking somewhere on your HD or what? Just curious

Why are uninstalled programs still there?virus

Technically no they don't...

A system restore works by taking literal ''screen shots'' of your pc and remembering what was present at the time.

It measures the request to any recent changes and matches it to what it remembers.

So technically yes a small amount of memory is used to maintain deleted software but the files all go.

Why are uninstalled programs still there?anti virus

Unless you wipe your hardrive completely, nothing ever goes away.
B-kwz uninstall does not necessarily mean delete.
use this every once in a great while,so its not possible for someone to recover anything.and the other two guys above me gave good answers so gg,and use this program if you dont want anything personal to be recovered.
yes. look it, all the archives,programs that you unistall never are erased. this files are eraser a logical form but not phisical form, because they are hide some place of your hard disk.