Hi,
well im new using linux so i need lot of help.
i installed Red Hat enterprise linux server 6.4 on my pc.
Lenovo 6075E2S
Processor: Intel Core 2duo 2.66 ghz
Ram: 4 gb
Video: Intel GMA 3100 integrated
Audio: Soundmax integrated

initially it runs from inittab id:3 (CLI mode) but i changed it to id:5 (GUI mode).
After that i reboot system but i keeps loading the OS. the screen shows me black screen with the white loading line totally completed but it freeze there.

the GUI dosnt load.

You should try to boot in single-user mode (you do that by entering linux single at the boot prompt), or
boot your system from the install CD. Then, edit again inittab to put back id:3 and reboot.
You should then be again with the CLI mode. You can then log in, and try to launch the GUI by typing startx or xinit.
Note carefully what is going on, and if something goes wrong kill the X server by Ctrl+Alt+Backspace.
Then, try to look at the file /var/log/X.log (or similar name). This will tell you what is causing the X Window system
to fail at startup. Check also the file /etc/xorg.conf and look in particular for Section "Device" in that file.
You can also try to start X by the command xdm -nodaemon & (typed as root) in CLI mode.
If everything is right when using startx/xdm, it means that 5 is not the GUI mode. You need to look at the RedHat (or equivalent CentOS or Scientific Linux) documentation to identify the proper runlevel.
If startx works but not xdm, you may have a problem of xdm/kdm/gdm configuration.

Its entirely likely you selected server install, which doesn't install GUI; most serious servers don't bother (they don't have monitors attached when rack mounted).
Try going back to the cli & 'startx' cmd as recommended and post the msgs.
You could try installing the GUI (as root user)