Why cant the search feature accept terms 3 letters or under?

Did you try using asterisks?
e.g. iPod *zip* cases

As 'tntracy' replied to a previous query about this same problem I will quote him -
"Currently, as you have discovered, the minimum search word length for the forums is set to 4 characters. The trade off here is if we shorten this, the search index, and the vBulletin database, both take up significantly more storage space. So, I do not want to arbitrarily change this parameter without first discussing it with Dennis Lloyd, the owner and publisher of iPodlounge."

For the time being, try the following workaround. Search on "*zip*" (without the double quotation marks). The asterisks are wild card search characters, so this will search on "zip" preceded and followed by any characters, including spaces. I just tried it and it works - the search engine treats the wild card characters as part of the length of the search terms, so they make each term the minimum 4 characters long.