After i had an accidental replacement of one of my bars in the boot screen with a different colour palette, although it looked fine in Windows, after i applied it and rebooted to see it, the screen came with awful colours, nothing like it looked within Windows! Not to mention that some screens give the blue screen in your PC, forcing you to boot into safe mode and change to something else... what a loss of time and effort! I thought there must be an easier way... and there is!
I use VMWare to run a virtual WinXP Pro environment and that environment is not important at all, i mainly use it to test software, surf the net safely, etc... it is basically a sandbox. Hence i proceeded to install BootSkin and test my custom screens there! Not only it takes 1/3 of the time to boot, you can check your screen what it ACTUALLY will look like, and if you get the dreaded blue screen, it is much easier to revert, or even format the whole darn thing again with no worries of data loss or anything else.
I know that not everybody is using VMWare or can afford to buy it, but there are several virtual machine applications out there for free! So if you are really into creating and testing then do your self a favour and grab one now! (If i remember correctly Microsoft have one such application for free).