The resize bar gets combined into the taskbar which can make for some strange effects. The best way to go is make a stand alone version in Skin Studio. You can open the imported one and add new graphics, change the button's dimensions etc. but you'll get all the WinXP skins stored with it. I had to do this to get an OB skin for SETI green because it didn't import well.
After you save the skin as an OBpack you can go in manually and delete all the extraneous stuff and manually rewrite the OBtheme & OBskin files to make it work as a stand alone theme. You'll also have to make a screenshot for the list in the theme changer. Look at a theme that wasn't converted from an XP skin but still has the XP look to see what files you need to keep and which ones you need to delete. The directory structure is a little weird. The SETI green OB theme would be a good example for how it should end up. The OBtheme and OBskin files are text files just like a UIS file, so you'll need to setup the paths after you change it from a converted skin.