Hi,
U could have better received the answer in some windows forums.I tell you later "why".
When you dual boot a system with windows being one of it,
the boot sector is modified by linux & a pointer to the grub.conf file is created (pointers to ntldr i.e windows bootloader is removed in the process).
Grub in turn knows, where to look for window's boot files & linux boot files. & redirects BIOS as per the choice made by user.
Now..... U deleted the liux boot partition & in the process deleted grub.conf.So when the pointer tries to find grub.conf it's unable to recognize even the FSystem,leave aside loading grub.conf.
& So the same it says:-
GRUB Loading.
error: unkown filesystem
The Solution:-->Now that linux partitions are not there so rescue CD wont help.Instead u hv to boot from vista CD & find commands to fix the mbr & boot files.
As of WindowsXp i know there are commands available when you boot from the CD in
"Recovery Mode".These commands actually modifies the MBR of HDD & remaps the windows boot files.These commands are "fixmbr" & "fixboot".Not very sure if the same commands or the same functionality is available on Vista.
So you need to consult some Windows forum or google it out.
