I have an 18gb hard drive that I partitioned 10gb for my Windows installation. When I installed Mandrake 10, I used about 7 for the main linux partition and the rest for the swap. My problem was that when it asked where I wanted to install the bootloader to, I chose to put it at the beginning of the / partition. However, when I restarted, the comp just booted into Windows like it would without any other OS installed. Should I have installed the bootloader to the MBR, and if not, where should I put it?

Using a LiveCD, run cfdisk or fdisk or whatever partition utility it comes with. There will be an option to toggle a certain partition bootable or not. Make the windows partition not-bootable and make the linux / partition bootable. That should solve your problems.

--EDIT--

You should keep it on the linux / partition as that is the safest thing. As long as that partition is bootable and not the windows partition, you should be all set. Make sure that you have an entry for windows, too. Here's how it should llook for lilo:

other=/dev/hda1
table=/dev/hda
label=<insert label of your choice here>

What's this LiveCD that you say I need to use?

No need for a liveCD.

Boot the Mandrake 1st install CD and select rescue mode. Do not mount the partitions. Then use fdisk or cfdisk to change the boot flag.

I tried using the 1st install cd for Mandrake, but this just ended up making me reinstall. The good thing, though, was I did this and just put the bootloader on the MBR this time, and the dual boot now works great.

OK, so you solved your problem, but for anyone else that has trouble, here's a solution. Not sure how it works with Mandrake, but I have made this work with Slackware. I'm sure it works with Knoppix, too (I always keep a copy of it, for rescue reasons). The way to do it with Slackware (you could have actually popped the Slackware install disk, or any install disk for that matter, in and used it, even though you're using MDK) is you just hit enter at the boot: prompt, then log in as root, and type either 'cfdisk' or 'fdisk' at the command line. Simple as that, then follow above instructions for toggling the bootable option. Fedora Core 1 used Disk Druid, IIRC, when I installed it a few months back, and I think you have the ability to use the FC1 install disk in the same way as I've mentioned for the Slack disk. Anyhow, happy trails.

All you needed to do was change the boot order in the BIOS.

How would changing the boot order in BIOS help?

Because the bootloader was installed onto a drive other than that with windows.

Assuming Windows is on HD0.
If the bootloader was installed on HD2, but HD0 is checked first in the BIOS, Windows would load, not the bootloader.

Windows may be on 2 and the bootloader on 0. But if 2 is checked first.... you get the idea.

That's the way I tend to do it as well

You've lost me as well

All you can change in BIOS is what physical drive to boot from. How would that help you when both OS's are on the same drive?

Maybe I should ask this, do you have more then one hard drive your system?

I assume that you do. Windows was installed on one of the drives.
Lilo ( the linux bootloader) was installed on a DIFFERENT drive.

The bios is set to boot the Windows drive first, therefore never getting to the bootloader.
Changing the boot order in the bios to the drive with the bootloader on it would have solved the problem.

Of course, if you only have one hard drive in the system then everything I said is pointless and I will shut up now.

It won't. I missed that part, so I will shut up now.

No prob, thought maybe you knew some trick I didn't. Thanks anyway