I have got some bad news
http://shop.ebay.com/items/_W0QQ_dmptZUSQ5fCSAQ5fWCQ5fJeans?_nkw=512+mb+computer&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=bell+1350&_osacat=0
Without the printer and scanner and software, you're looking at less than $50. With the software, if you're actually legally selling it and planning on giving them the install discs, you're probably looking at another $50 or so. Nothing additional if you're not giving them the discs.
Jasc is $19.99 new
http://shop.ebay.com/items/?_nkw=jasc+animation&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=512+mb+computer&_osacat=0
Corel paint shop pro is $38 new
http://shop.ebay.com/items/_W0QQ_dmptZUSQ5fSoftware?_nkw=corel+painter+x&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=jasc+animation&_osacat=0
The printer is basically worthless (no offense here, just is what it is, and that's old.)
http://shop.ebay.com/items/_W0QQ_dmptZUSQ5fSoftware?_nkw=lexmark+z23&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=corel+painter+x&_osacat=0
The scanner probably isn't worth hardly anything either, without the model I couldn't tell you exactly. But it's tough to even find a traditional scanner without a printer attached to it anymore. Even with that they're only $50 or $60 brand new.
So, all in all, try to get $150. See if you can get any suckers to bite. Seriously though, you'll be lucky to get $75.
This is why everybody's got old computers sitting in their basements.
Again, sorry for the bad news.
Oh, and one more thing. I saw someone say $1,000. Sounds like they haven't been computer shopping in a long time. Unless you're buying a mac, it's hard to even spend that much anymore.