Hallo,
At the moment I have Fedora core4 (64bit) and WinXP. I started using linux
4 months ago. Now I hope that in a couple of years I am going start looking
for a job as a linux administrator or programmer, etc. So apart from using Fedora, I would
like to start learning an industry standard distro. Is there any? I have heard that it is
Red Hat Enterprise Linux, and that Centos is just a free version of RHEL. Is that true?
If so, I would like to install Centos as the third operating system. As the boot loader I
use grub from fedora. After the installation, Is centos going to be recognised by grub automatically
or do i have to do something to boot it?
thanks

if you use fedora then you won't benefit from using centos, as fedora is 95% of redhat already.

for what you actaully asked though, centos's installation will pick up other preinstalled OS's just fine, but if you want to leave the existing bootloader in place you would need to manually add it to there. it would be easier to use centos's version of grub.

Don't see any difference in Grub between different distros. Everyone is as easy as the other.

Centos is a rebuild of the RHEL packages, and yes: It plays a big role in the industry. Now, you may want to look into Suse, as Novell is playing a still bigger corporate role these years.
Also, if you plan to work with this professionally, you can probably benefit from the Linux instructions from IBM's developerWorks. I learned a lot from their free Linux (LPI) certification tutorials.

Thanks,
I'd also like to know which areas of linux I should especially focus on to benefit
professionally later on (obviously apart from general learning of the system)
e.g bash, python, c, servers, etc.?

depends what you want to do... ideally you need to learn everything...

I thought that would be the answerhaha
The only two things that come to my mind are programmer and administrator

If you want to keep the Admin option open, learn how to install & config major services like Apache, email, ftp, Samba, ssh etc.
Learn to prog in bash script and in Perl (which can be used both for admin scripts and apps).
You should also learn at least 1 SQL DB eg MySQL.
However, it really depends on what you want to do eg SysAdmin/DBA/Sysprog or Apps Prog (in which case look at C/C++/Java).