whenever i try to change the bootskin ,it doesnot wors out.i installs the bootskin software and selects a skin, but on booting it asks whether you wants to start normally or use previously worked one, i had to select the later as the first one doesnot works. is there any other way to change the bootskin. thanks.

1st, what application are you using for your bootskin?  I use Stardock's Bootskin (http://www.stardock.com/products/bootskin/).  There are currently 617 different bootskins available at http://www.wincustomize.com. I REALLY like their "Logon Studio" though (You can use Both!).  I would suggest you uninstall, use Regvac, reinstall and try again.