I have a few used computers, is it safe to sell them, and what's the best way to do it?

I have 3 used computers: a Packard Bell from 1996, a Dell from 1999, and an HP from 2001, that I don't need anymore and I want to sell them. My parents first told me to sell them, but then they told me that even if you reformat the hard drive, someone can get your personal data from it, so they told me it's not safe to sell them. First, is this true? I know how to reformat the hard drives and restore them, but if I sold them afterwards, would they really be able to somehow extract our personal info? Second, what would be the best way to sell them? I know I can post an ad on craigs list or whatever, but how do I figure out what's a fair amount to sell each for? I have about 3 weeks to do this before I go back to college, I'd really appreciate some help on this!

I have a few used computers, is it safe to sell them, and what's the best way to do it?norton

Ok here is what you do. You restore them and make it look like a new computer then your clean the outside so it looks pretty new then sell them On Amazon, Ebay or sell it to one of your close friends

I have a few used computers, is it safe to sell them, and what's the best way to do it?spyware remover

how much do you want for one of them(a desktop)?, who cares about your info.?
Check sold item prices on Ebay that will give you an idea
get the low level format utility that works with the manufacturer of the hard drive. it should erase everything. regular formatting with an os will leave traces of files. low level formatting can fix it. it removes any file system that was there. even after formatting like that you have to fdisk and format again with a file system.
when you reformat you delete all what was on the hard drive
If you format the hard drive, EVERYTHING WILL BE DELETED, and you'll have t REINSTALL windows. No personal data will be left 100%! That is a lie! I'm SURE OF THIS! AND the selling stuff, of course it's safe. Go on Ebay, and there you go!!! The amount you figure out, IS you judge yourself, it depends of how much your hard drive stores, how much RAM memory you got, and how much is your processor's speed! BUT, it's safe to sell. You don't have to worry about the personal data, that's a lie. EVERYTHING will be deleted when you format. When installing windows, do a FULL FORMAT, and that's it.
I would downlown this program called eraser it is a www.heidi.ie/eraser it will do xxxx's and ooo's to wipe your drive.