When I log In as root, I can enter /fat-c (i.e NTFS format drive), but I want to enter inside it logging in as user also. How to do that?

I'm using both XP and SLACKWARE.

The mount point /fat-c where you mount windows drive may not have proper permissions set for normal user to read write or execute. As root change the permission for the mount point but beware of what you are doing.

Are you talking about entering the drive to read and write files? You don't need to do any extra login for that...

Please give some more detail on what you are trying to do.

can you paste your entry for the windows partition in
/etc/fstab? Just run this, then copy the output:

grep '/fat\-c' /etc/fstab

also, paste the contents of the file /etc/group

cat /etc/group

###################
there are certain options you need in order for an ordinary user
to mount and access a device
and the user must be added to certain groups (such as disk, ...)

Yes, I want to enter inside it for reading and writing.
I can do it logging in as root, but now I want to do it by logging in as normal user also.
I don't want other users for doing this. Only for the user solitude (this is the user account that I'm using).

Is it risky?

Change the permissions for the mount point or else change the ownership. But do it carefully. I hope you know what you are doing. It shouldnt be a problem writing to a ntfs drive as such though.

Can anybody suggest me clearly, is there any risk for doing this.
Is there any side effects.

And how to make it accessible. Please somebody provide me step by step
guide.

I'm totally confused

Most Linux distros will read and write to NTFS with no problem. As long as you have your data backed up, this is not any riskier than any other routine operation.

Whereever your NTFS partition is mounted, do "ls -l" from a terminal. This will show you the existing permissions. Here is an example:
drwxr-xr-x. 2 mherring mherring 4096 2009-06-22 15:38 Pictures

This says that the directory is owned by mherring and assigned to a group with the same name. The owner has full permissions, but everyone else has only read and execute. Suppose I wanted to give write permission to the group. I would issue one of the following commands:
chmod g+w Pictures
chmod 775 Pictures

The change the directory (mountpoint) AND all the contents, add the -R option.

For the details of this syntax, look at "man chmod"

There should also be a GUI control panel for this somewhere in your menus.

if you want 'solitude' user to be able to mount
you need to
1. add this user to certain groups such as 'disk', etc.
to do that,

edit (as root) the file (before you start editing make
a backup copy: cd /etc; cp group _group)

/etc/group

Look at the lines that start with

disk:
floppy:
cdrom:
plugdev:

if you want solitude to be able to mount a disk partition,
..., you must add solitude at the end of each of these lines
after the last colon
If there's already an entry like probably root precede
solitude with a comma (no spaces)
so for instance
the original disk:.... line might look like

disk:x:6:root,adm

and after editing it should be

disk:x:6:root,adm,solitude

Now, if you want to have the windows partition automatically mounted
at boot time, add en entry in /etc/fstab for it

I don't know the device name of your windows partition.
But there are good chances it's /dev/sda1 (if not replace
appropriately). You said in your message that you want it mounted
in /fat-c, so I'll assume that /fat-c exists

edit (still as root) the file /etc/fstab
Add an entry or edit the existing entry for the windows partition

Now, your entry for your windows partition should
look something like:

/dev/sda1 /fat-c ntfs-3g users,noauto,noatime,exec,rw 1 1

If you want solitude to be able to write in the windows partition
as root you can change ownership of /fat-c, so that solitude is
its owner:

chown -R solitude /fat-c

Now to your question: is it risky?
The answer is yes. It's always risky to give write permission
to an ordinary user. You can inadvertently delete some
important files

First you need to know the partition of your Windows partition.
Assuming that your partition is mounted to /fat-c, open /etc/fstab in a text editor as root and the entry should be something like:
/dev/xdx /fat-c ntfs-3g umask=000 1 0

to try it type # at the beginning of the existing entry for the "/dev/xdx" in question and add the line as above.
Save your file.
As root: umount /dev/xdx
then: mount /dev/xdx

Now try to see if you can enter into /fat-c as a user.
BTW, a suggestion: it might be better to rename /fat-c to /ntfs-c since it might become a little bit confusing and to keep things clear.