I ran into this problem recently when setting up BootSkin for Windows XP on a old laptop that has Windows 7 as a primary OS. I recently solved this problem so posting about it here to help people in the future who may and try and search for a solution to the problem as I'm sure it may come up for them.

The original problem was that if you have XP as a secondary OS on a computer that changing the boot skin has no appearent effect. This may not occur in all situations as it may depend on how XP was added to the system.

In my case I had used a third party tool to add XP to Windows 7's BCD and boot.ini file. This was where I ran into the issue.

If you run into this problem the fix is simple. You have to edit the device path and bootloader path for the XP install to point to XP's ntldr file on the root of the partition that OS is stored on. Be sure the boot.ini file located on that partition is setup correctly too!

You can either use bcdedit to do this or in my case I used visual BCD Edit. There was another tool called EasyBCD that I originally used to add the XP install to the boot menu. But that program doesn't seem to let you alter the bootloader path. It seems to create a bootloader in NST folder on main boot partition of the primary OS you have EasyBCD installed on and in this case this is what breaks BootSkin.

So when using visual bcd editor go to the Loaders section find your XP entry and change the Device Path to match the partition your XP install is on then go to the bootloader path entry and change it to point to \ntldr instead of the NST folder path EasyBCD might have added for you.

Upon doing this this fixed that issue for me and may help in fixing it for you if you have a non standard BCD setup for your XP dual boot install!