i agree with nia (and bob too). i like to see the old threads about what people sold it for, and whatnot. and the mods don't have time to deal with deleting anyway.
so i'd suggest:
1. always use FS (for sale) and WTB (want to buy) in your headers, along with a concise description of what you are selling or wanting to buy.
2. if you have a pending sale, either add a post saying that, or edit your original header to include "SALE PENDING"
3. once it's sold, edit your original post to include "SOLD" after the description.