Get a second drive. I purchased a Maxtor 120gb unit from OfficeDepot. Hopefully they'll actually cough up the rebate check.

You may want to get a kit for installing the drive. I ordered one from Weaknees. This will give me not only a solid mounting but cables and a pair of new fans to keep the unit cool. But for now I've hacked up my own mounting from an old set of PC rails.

Then, open your DirecTivo and remove the drive. Some instructions (in PDF form) can be found here.

Get and burn the mfstools.iso. This contains the tools needed to tell the Tivo about your new drive.

Get an old PC that can boot from CDROM. I shanghai'd Chris' ancient P2/350 box for the task. Make sure it has a single FAT32 partition on it. You'll use this to store a backup image of your existing drive.

This is important, do not skip the step of making a backup of your drive. I'm trying all sorts of hacks and as they fail I just reload the backup image and I'm back in business. My backup image is about 1.5gb in size.

You need two IDE addresses. I put the original Tivo drive on the secondary IDE bus as the master device. I then put the new drive on that same bus as the secondary slave device. I booted the box and got into it's setup. There I told the machine to boot from CDROM. I also checked to see that the machine saw the two drives and understood the right sizes for them. This is important as well, some older boxes might not be able to properly understand some of the very large drives. Save yourself untold anguish and don't try these steps on a box that can't at least see the drives at their correct size. Really, it's not worth the hassles.

Then I booted into the mfstools CD. I told it to mount the local FAT32 partition and to do a backup from the original Tivo drive. Do not skip this step. If anything goes wrong the backup can be reloaded onto your original drive and you can start over. The steps for making a backup depend entirely on your PC's existing configuration. Mine happened to have a FAT32 partition as the first one on the drive. Yours may not and you'll have to check it for yourself. I will not go into the details here, see things like the Hinsdale HowTo for more info. What you're doing here is telling the system to mount that FAT32 partition onto a some part of the current RAM drive that the CD booted into. You then tell the mfsbackup program to pull from the original Tivo drive into a file on that FAT32 partition. Make sure the partition has at least 2gb free on it before doing this.

For mine the commands were:

mount /dev/hda1 /mnt/c
mfsbackup -f 9999 -6so /mnt/c/directv-backup-20031203.mfs /dev/hdc

I basically told it to mount the C drive as /mnt/c and then put a file named 'directv-backup-20031203.mfs onto it as an image of the /dev/hdc; secondary IDE master, drive. If you don't have standard drive setups you WILL need to do your own checking to make sure of which drives got mounted where. Hinsdale and other faqs cover how to do that.

From there it was a simple matter of telling to "BlessTiVo /dev/hdd" and then "mfsadd -x /dev/hdc /dev/hdd". These two steps tell it to accept using the new drive (on secondary slave as hdd) and then expand the Tivo storage to include both drives. Shut down the PC and remove the drives.

Put the drives back into the DirecTivo. Make sure you get the IDE cable set up right. The blue connector goes into the motherboard. Make sure you get it right. Also, everyone's instructions warn you about not dislodging the white front panel cable. Apparently if you do and you turn the box on, it'll fry the front panel board. Word to the wise, don't screw up the white cable. Once you've got the drives installed, boot the DirecTivo. It will take quite a while to get itself sorted out. It'll show the gray powering up screen for several minutes. Followed by the 'hang on' screen. It'll then show the DirecTV splash screen and spend even more time downloading data from the satellite. In all it seems to take about 15 minutes or so for this process to complete.

Once it's downloaded everything it needs you can confirm your new recording size by pressing the DirecTV button, navigating into Messages & Setup submenu and then into System Information screen. Scroll down and look for Recording capacity. It should now show you a much longer amount of recording time. Mine went from 30 hours to over 140.

If everything went well, navigate back one screen and select the Retart or Reset System option. Restart the box and pull power from it as soon as you see the screen go back into the gray 'powering up' screen. Now put the lid back on the box and you're all set.

Again, a note of caution. You can do yourself and your DirecTivo egregious and permanent harm here. The inside of the box has high voltage in it. Touch the power supply while it's live or while it has a stored charge in it's capacitors and it may very well KILL YOU. But this is true of any electronic device so if you're not comfortable working inside high voltage devices then DO NOT PERFORM THIS UPGRADE. Likewise, if you get the drive parameters wrong you could lose use of either the PC, the Tivo or both. You're doing some stuff that interfacing directly to the hard drives here, there's no hand-holding in the software. Get it wrong and you're screwed. Don't say I didn't warn you.

Frankly, this isn't much more complicated than sticking a drive into a PC. The only real personal injury risk is from the bare power supply inside the Tivo. Your PC should have a shielded supply so it's less of a risk to your health. I'm not saying there's no risk, just less. Also, avoid mishandling the hard drives. They're fragile devices. Do not manhandle them. Do not bump, jar, hit, drop or otherwise do anything other than gently move them around. Treat them like they're extremely fragile and you'll be fine.

Read my instructions several times. Read the Hinsdale HowTo as well (it's what I followed). Once you've read and understood everything give it a try. If you have questions, do not nag me about them. I'm no more an expert than anyone else here. Try the DealDatabase NEWBIE TiVo/DirecTiVo Hacking forum if you run into trouble or have questions.

My next step will be to hack into it and get it to understand how to use a Linksys USB ethernet device. That's apparently a lot more complicated. I'll try to summarize it here once I get it to work.