Actuly i h;ve change my monitor so Linux boot properlyy but login screen dos't appear except blank screen so pls guide mee wht to do........i get in to non gui buy pressing ctrl + alt+f1 and after given user name and passward i don;t wht to do next i h;ve red Hat distribustion any1 who can help me in easy wayy.........soo plss as soon as possible i will be thnkful to uuuu....coz my work has been stoped due to this....

You can try typing the "startx" and see if that will get you to a GUI.
"init 5" might work too. I have used both of these commands to get to a GUI and had them work.

No sorry, this will not work for you. What is happening is this:

You have a new monitor installed, and the operating values are different from the old one. I never got to solve this (I ended up doing a reinstall, because I didn't have the time to play with it). But here is what you should do to reestablish your GUI:

edit the /etc/X11/XFree86Config file or something like that, I forgto what it is called. It contains all the info for the GUI(the X) to start. Locate the Monitor section, and try to set in the correct values for the Vertical refresh rate and Horizontal sync. Also set the resolution for your monitor. I DON'T HAVE TO REMIND YOU TO MAKE A BACKUP OF THE FILE first.

Well, once you do this, restart the computer and hope you got it right I never did, but I didn't have the papers of that monitor, and had no idea what values to type in. IT should work if you type in the correct ones.

One more thing... Have you tried loging in as root and typing startx?

You probably alreadi are in init 5(to test this, press CTRL+ALT+F7) and that should get you to a blank screen, if your gui isn't working.

Well, good luck!

Peace!

I use both commands with init 5 nothig appear but when i type startx than message appear like this "Server is already active for display Error" and fatal Error apper...and when i try tou reinstall it and boot from my cd there only 2 options clean installation and upgrade and whn i try to upgrade option it ask from me about bootloader only....so kindly suggest me wht to do now.....

Ok, X is already up then. Have you tried Ctrl+Alt+F7 ?

Yes but same result my monitor lights start blinking..........

Sounds like your monitor isn't coming up because you're trying to use a resolution/vert-horiz range that it can't handle.
Look for a manual that came with the monitor, or you can try looking for the specifications online and edit them correspondingly in your /etc/X11/xorg.conf or /etc/X11/XF86Config

Hope you can use an editor in console, which I assume you probably can. If not, for just this one, I'd use pico if you don't want to take the time to learn vim/vi/emacs et cetera

Or you could try xf86config, or xf86cfg. whichever you'd like. unless you're using x11, then you'd use xorgconfig, or xorgcfg.

Use trial and error just to get it working, and then tweak for perfected results afterwards.
EDIT: You could also first try Ctrl + Alt + +/-
+/- being either of the + or - keys, this will change your resolution. If it's a problem with resolutions, this might just be good enough to 'get it working'

Good luck

Dear thank u veryy much i got the Gnome screen just by pressing Alt+ctrl and +/- thank u veryy much once again...........

Nice

Yep, it's no problem.