Thanks for the advise sir.
yesterday, I didnt install gcc compiler at all, which caused all those problems.
So i clean installed FC7 again in a fresh partition, (19GB) in which i used 12 GB for /root mount point, 1.2GB for swap space and remaining space I left free for using in Windows XP.
But now after the grub loads, i cannot get into fedora .
I am getting the error
Kernel Panic : VFS unabe to mount root fs on unknown-block(0,0)
I even wiped the RAM off static charges, but in vain. the error persists.
I want to know how to bypass this error, or bypass RAM support initially.