ntfs-3g is installed now the grub2-mkconfig command is working.should i add the menuentry to:
i removed the entry i made in 40_custom after installing should i add the menu entry to '40_custom' or run grub2-mkconfig command.

run grub2-mkconfig and see if it picks up windows, if not then make the 40-custom entry then rerun grub2-mkconfig

i ran and it pick up windows 8 but it doesn't show up in the boot menu.
then i ran the command ,then too the boot sreen wouldn't show windows eight.
should i copy the menu entry for windows8 as it appears after the grub2-mkconfig command is run.

I don't understand what went wrong with the second attempt you just described. (I assume you already understand what went wrong when you didn't have grub2-mkconfig store its output in the right place).

Whatever went wrong, won't be fixed by copying that menu entry. If I understand your intent, you would be copying it from the output of grub2-mkconfig back to the input of grub2-mkconfig (which would not be at all helpful).

What do you mean by "boot screen wouldn't show windows"? (How experienced are you with grub?)

The default for grub may not be showing any menu at all. You might need to press a key at the appropriate moment during startup to even see the menu (or you could change some other setting to make displaying the menu be automatic).

Mainly I'm saying that before someone helps you understand why you don't see the Windows line of the grub menu, it would help to be sure you are seeing a grub menu at all.

I meant the after running the 'grub2-mkconfig" command the grub menu list was supposed to be updated right?(i am only sparingly experienced with grub)

would this command store the output in the right place that is in '/etc/grub2.cfg':

should be If I'm not mistaken.

no your not mistaken it worked.thanks everyone.

how do i make the windows8 entry in the grub list first so that it boot up after the countdown.

edit the GRUB_DEFAULT line /etc/default/grub I don't remember if it counts from zero or one to the menu entry you want for the default. I think you can set it to menuentry name also.

i opened the file and here whats set GRUB_DEFAULT=saved.should i replace the saved with the windows8 menu entry name?

Yes, will be something like this What the menuentry for windows is label in your grub.cfg
then rerun

i changed it to,
as gave me a syntax error.
should i specify the number of the entry?

If the doesn't work

It worked when