When ever i try to install red hat linux enterprise 5 from usb device...it is not showing my harddrive for installation target...it is showing only my usb drive..and nothing else.

Ok..and if you provided any details about your hardware and what version of RHEL5, what kind of USB drive (external HDD? Flash?), we might be able to tell you something.

As such, you're using RHEL...have you contacted RedHat support? You are paying for it, since you're using RHEL, right?

I am not paying for this rhel...i just got an ISO image from one of my frnd so i started to learn red hat linux..I dont the version of my linux it is just Red hat linux enterprise edition...and my system configartion is Harddisk-320 gb,Ram-3 gb,Ati graphics card,Intel core 2 due CPU,T6400 2.00 ghz

And my Linux version is Red hat Linux server release 5.1(Tikanga)..and i am using sandisk pendrive its of 4gb

If you're not paying for it, then you shouldn't be using it. You will NOT get patches/updates/bugfixes, etc., and chances are you'll need all of that. If your goal is to learn Linux, you can load ANY version (Ubuntu, Fedora, Debian, openSUSE, etc), and learn. If you NEED RedHat Enterprise, you can load CentOS or Scientific instead...they are 99.5+% identical to RHEL. You can learn the same things, in the same way.
That's great...but the details we'd need would be things like

• Can your system boot from a USB device?
• If so, is your BIOS set to boot from USB first?
• What kind of hard drive controller?
• If SATA, have you toggled the mode in your BIOS?

And I'll say again that unless you're paying, don't use RHEL. Take note too, that RHEL/CentOS/Scientific are meant for SERVERS, not consumer laptops/desktops. Think about what a server is...it typically doesn't have sound cards, bluetooth, wireless, webcams, or any of the other types of devices that you may want to use. The new RHEL6 doesn't even come standard with a GUI...just text-console, since that's not needed on a server. Consumer-distros like Fedora, openSUSE, and Ubuntu are better choices. You can learn Linux with ANY version.

I get your point but i was trying to learn these things...like making server's etc...i How they work...and all that....Becz i am going for the examination of this RHCE may to learn this we need RHEL server (I don't know that much)..

And i can boot from usb drive also and my bios is set to boot from usb drive .
And my hard drive is IDE ATA/ATAPI controllers.
And when i boot from usb it loads all the things but when i come to target files for installation of linux it is not showing my harddrive it is just showing usb drive only. i checked about advanc also but i got nothing from it

Try CentOS, it's RHEL without the branding and such, anything you can do with RHEL you can do with CentOS and the information you learn working with CentOS translates to RHEL pretty much perfectly.

okk thanx...and that cbt nuggets for linux they can also work on centOS ?

You need to spell out your words.

And "making servers" can be done on ANY version of Linux...postfix, sendmail, samba, etc., all work on any version of Linux you can name.
Well again, a consumer-grade system may not work with RHEL, which is why I recommended a consumer-grade distro to learn on. And again, CentOS or Scientific are almost identical (said that in my first reply), so yes, what you learn there will transfer to RHEL certifications.

I'll add my advice for CentOS. It's true that RHEL may not support all the hardware that you have on a home computer, but that's not because it's only for servers: they do separate server and desktop versions. It's because computers aimed at home users may have components less common on those manufactured for business. CentOS add extra drivers to correct that (Scientific Linux doesn't). If I put RHEL on the computer I'm using now, I'd have no sound, but CentOS was fine. You can certainly learn about servers with CentOS, for it's actually the most-used Linux on web servers.