I wondering if there are any open source programs to create skins for Linux. What i am looking for is to create skins like these one that winblows uses.
There's lots of themes for linux which change it's appearence, and of course each of these is completely configurable. Take a look at http://www.gnome-look.org/
You can install all types of eye candy with programmes such as gdesklets or superkaramba.
Also is there any program to change the boot screen and answer the startup screen where you enter user name and password like these :-
It's built in. Just go to Desktop>Administration>login screen. You can download other gdm themes from the gnome-look site as well