This isn't going to help you (in the short term) so don't hit me with a hammer.
When I first started using Windows 7 I hated the new taskbar. However, after spending some time using it, it actually is much better than that of XP. So, I think you shouldn't look back to making it look and feel like XP. I don't think there is a way to configure the taskbar/start menu to look like XP as it has been re-designed rather than just improved in this new version.
There's an application to bring about a start menu similar to that of XP/2k..... but it doesn't REPLACE the original Start menu... it just adds another one to the taskbar. I'd have to agree with ming... you may not like it now, but it'll grow on you.
Why exactly don't you like it? 2k/XP/Vista didn't have Aero Peek which allowed you to see what was in a window just by hovering over it's logo on the task bar. System tray icons are managed a little better, automatically hiding them to minimize the amount of space taken up. The start menu, although rather similar to Vista's, allows programs to also have their own list of recently opened files, such as Photoshop keeping a list of images you opened. It's also quite easy to search for a program or file right in the start menu.
My problem is how my little short cuts are now also bars when I click them. If I could seperate the two and just have the short cuts remain there and the bars on a seperate area I wouldn't mind.
How did you get used to this?