OSX, or XP?
OK, so a friend of mine asked me how did I turn my XP interface into a Mac recently, so here it goes:
First, you have to download iSkin at theiskin.co.nr - follow the instructions in the package (if you're confused as to how to use this or that, ask me) and run the Flyakite OSX installer, which is bundled in the package. The Flyakite only comes with a Tiger skin, but there are a lot of Leo skins out there that you may try.
The taskbar part is something of a challenge; ObjectBar is fine, but it isn't free, although there are some alternatives like WinMac.
Download ObjectDock from stardock.com, and find a decent Leo dock theme (Google or Yahoo search it).
As for the Explorer theme that mimics the Finder app in Leopard, I'm not really that sure about it. The setup that I did to my Mac OS/XP install still has the default Explorer interface, since any more changes to my PC and other people might find it a pain to use.
For the desktop icons, cut and paste all of the shortcuts to a safe location (My Documents or similar). Go to Display Properties, click on the desktop tab, and then click on Customize Desktop. Untick all the check boxes. As for the Recycle Bin, you can use a free utility called TweakUI to get rid of the icon. Click on the Desktop section, and then untick Recycle Bin.
Here's another tip: Try the GDI++ utility which can be downloaded at http://www.sendspace.com/file/ugit9x - this will make your fonts more Mac-like, just like what Apple does to your fonts in OSX.
Results may vary depending on the user. I'm not sure about the window buttons, though...
God Bless and enjoy your Mac... ;D