I'm looking for an open-source, simple and lightweight ecommerce system that is easy to modify to match the rest of the site.

I've already tried oscommerce, but trying to make it look a certain way is a nightmare.

Litecommerce seems to be what I want, but it is coded for PHP 5.3 and my webserver is at 5.2.

If anyone has had good experience with one of the systems out there, let me know.

Simplicity is a must. I'm not looking for statistics readouts on the admin console or anything.