Firstly, you need to know the wireless chipset your card has. You can't necessarily tell this from the make/model. Open a terminal and become root. (Type 'su -' - without the quotes - at the prompt and then type in your root password when asked.) Now type in the command 'lspci' (again without the quotes) and look for a line with 'wireless' and/or '802.11' in it. It will identify the chipset. Post that line, and we can go from there.
A little food for thought. Mepis includes a number of proprietary drivers, which is perhaps why it detected your wireless card when other distros didn't. Mepis takes a more pragmatic view of non-free (as in speech) software than other 'purer' distros. Ubuntu is all open-source but makes access to non-free fairly straightforward. Fedora is by policy strictly open source, and you have to be willing to lift the bonnet and get your hands greasy for a lot of things. Seems to me that both Mepis and Ubuntu are good choices for Linux novices - Fedora somewhat less so. One thing to bear in mind. A new release of Mepis (Mepis 6 - where did 4 and 5 go?
) is due within the next two weeks. It's borrowing a lot from the latest Ubuntu, so you might want to get hold of the new Mepis. Hopefully, all the polish of Ubuntu Dapper and the pragmatism of Mepis.