Here is an example grub.conf:
# Nick's GRUB config
title=Gentoo Linux 2.6.17
kernel /boot/linux-2.6.17-gentoo-r4 root=/dev/hdb3
The "default 0" line tells GRUB which entry to boot as the default. 0 corresponds to the first entry, 1 to the second and so on. So here, the default is Gentoo.
"timeout x" - x is the number of seconds to wait before booting the default.
The "splashimage" line sets the background to the image specified, clearly this is optional!
Now on to the important info: GRUB counts disks and partitions from 0 using (hdx,y), where x corresponds to the disk and y the partition. So, /dev/hda would be written as hd0 and /dev/hda1 is (hd0,0). For /dev/hda2, it'd be (hd0,1).
For your Linux entry, the root "(hdx,y)" line specifies the partition on which the kernel image resides. If /boot is not on a separate partition to / itself, then this will be the same as your root partition (/dev/hda2 in your case). The "root=/dev/hdxy" in the kernel line specifies the root partition. Since I don't have /boot on a separate partition to /, I have "root (hd1,2)" and "root=/dev/hdb3", i.e. those are the same.
The kernel line specifies the image name, so you'll want "kernel /boot/vmlinuz" if that's what your image is called.
So, your Linux entry should probably look something like this:
title=Slackware Linux 10.2
kernel /boot/vmlinuz root=/dev/hda2
Your Windows entry will probably be the same as mine, since I also have mine on /dev/hda1.
After editing the file, save it and run "grub-install /dev/hda".
Hopefully that'll work