I would suggest purchasing a copy of Windows XP (Get XP Home, it is cheapest), wiping your disk and installing XP. When Everquest is updated to work with Vista, you can reinstall Vista from the materials given to you with your new computer.
This is, I believe your only choice if you wish to play Everquest now.
I hate to recommend this course of action to people. I use a Mac, and people often think I do this as a way of poking at Windows users, but nothing could be further from the truth. Windows is a better gaming platform. I just hate to present such a stark choice.
If you cannot install Windows, take it to COMPUSA or someplace like that and pay them to do it.
I second that motion.
Vista is nowhere near ready for general use by people who use PCs as you do.
Stick with XP. You can probably get a WinXP SP2 install disk from just about anyone to use for the install.
As for your license, save a little dough and buy just the license Here at TrustPrice.com