Q1: I have Linux and Windows installed, but I can't boot Windows anymore, I tried some things with the bootloader but it doesn't work. Is it possible to reinstall Windows without removing Linux?
what bootloader do you use, lilo or grub?

yes you can install windows without disturbing linux, long as you know what is where on you disk(s).. know that if you reinstall windows it will overwrite the mbr. so if you have your boot loader installed to the mbr, you will have to boot from cd to get back to linux to reinstall the boot loader.

tell which bootloader and you might get some more detail.