I would like to take this opportunity to encourage users of old PCs (pre-2005) to take extra precautionary steps before installing Windows 7.

Otherwise, you could end up baking your hardware. Yes, baking, in the oven.

How I ended up baking my laptop:

I installed Windows 7 on an older Toshiba laptop (from 2004) with a GeForce Go 5200 graphics card. First, it was not recognized - Windows 7 actually decided to use the Standard VGA Adapter driver for the card, which forced me down to 1024x768 resolution and extremely slow rendering. Well, I decided to look for a driver. Toshiba didn't have one on their site, NVIDIA no longer supports the 5xxx series, so I ended up finding a shaky third-party (modded) driver and modded it a bit myself to get it to actually recognize my card.

So after all that, I installed the custom modded driver and it seemed to work great at first: I even had Aero Glass! But little did I know there was a major problem lurking in the shadows... A few days after installing the new driver, I start up the laptop and it starts displaying columns of random flashing characters (at the BIOS screen). Immediately I concluded that this was a video card problem - it had happened to me before, with a GeForce 4 Ti4200 card.

Great, so now I had a dead video card. I looked around the web for people who had experienced the same problem, and found one who took his laptop to a repair shop and the technicians there diagnosed it as a "BGA failure." So I looked for BGA-related problems and found what seemed to be a re-occurring theme on various forums: "bake at 375*F for 5-10 mins". Surprisingly, those who tried it said it actually worked!

But how does it work? The BGA (Ball Grid Array) is what a video chip is most often connected to. This thing is just an array of tiny balls of solder that can melt at very low temperatures (even 120*C). When the video chip gets insanely hot (like over 100*C), it can warp the BGA so much that the chip disconnects from the balls and you end up with the problem I had (random characters at the BIOS screen). The solution, apparently, is to heat up the entire PCB (in this case the motherboard) evenly at a high temperature, so that the solder melts and reattaches itself to the chip. The prescription, in my case, was to bake at 375*F for 7 minutes.

Of course, I had to remove anything that might melt or explode - like batteries. I made sure to remove even the CMOS battery and remove all attachable parts (RAM, hard drive, etc.). I only baked the actual motherboard. But at the end, it worked! The video is fixed now, thanks to BGA baking!

The problem was caused by Aero Glass overheating my card. I'm 99.9% sure of it. And I'm also 99.9% sure that's why NVIDIA doesn't have any official Vista / 7 drivers for it. So immediately when I booted up my laptop after baking, I booted straight into Safe Mode, removed the graphics driver, and rebooted into Windows 7. Then, I reinstalled the graphics driver and made sure I was on the Windows 7 Basic theme, without Aero Glass. I also disabled the DWM service, so that there is no freak occurrence where Aero Glass gets re-enabled.

Precautionary steps that would've saved my behind:

Like I was saying, with Windows 7 on older hardware it's very important to take a few extra precautionary steps:

1. Run the Windows 7 Upgrade Advisor. Ensure that your essential hardware (the stuff you can't boot up without) is supported.
2. Take an inventory of your hardware. For me, the easiest way to do this was to just run Dacris Benchmarks (version 8.0) and create an HTML report under the System Information tab. This makes it much easier to find drivers online when everything in Device Manager is listed as "Unknown." But, if you have perfect memory, you don't need to do this.
   
3. Make sure you download any necessary network adapter drivers before you install Windows 7. Otherwise, you won't have Internet access. Usually the Windows 7 Upgrade Advisor will tell you if you need to do this, but do it even if it doesn't tell you - just in case - unless you have another PC connected to the Internet and a USB key.
4. For hardware that is shown as not compatible in Windows 7 Upgrade Advisor, try to find official Windows Vista drivers for it. If no official Windows Vista drivers exist, and the device is essential, you may want to reconsider upgrading to Windows 7.
5. For software that is shown as not compatible in Windows 7 Upgrade Advisor, try to find a newer version online that supports Windows Vista. If no such version exists, and the software is essential, you can still upgrade to Windows 7 but the software will probably need to be run in XP Mode. While XP mode is great, there are some things it can't do - like Direct3D. So if the software in question is a game, you may want to keep Windows XP. In that case, I would recommend dual-booting Windows 7 and Windows XP.

Now, in fairness, I couldn't have run the Windows 7 Upgrade Advisor on that Toshiba laptop I mentioned, because it had no working OS at the time (the reason I installed Windows 7 was because XP died). I should've really just reinstalled XP and then run the Windows 7 Upgrade Advisor.

A side note - hardware manufacturers (especially NVIDIA) have failed us:

While I was thinking about baking my graphics card, I had a thought: was it really the fact that Vista had such a different driver model that caused hardware manufacturers to produce unreliable drivers? Did hardware manufacturers really not have enough time to adapt to Vista? I remember Microsoft in 2005 mentioned that any PC made in 2005 or later would be able to run Windows Vista. So hardware manufacturers in fact had 2 years to produce Vista drivers. The Vista development cycle lasted 5 years. Plenty of time for IHVs to get involved, learn the Vista driver model, and develop drivers in consultation with Microsoft.

So who really failed here? Microsoft? Was NVIDIA's discontinuation of support for the GeForce 5xxx line a Microsoft decision? Who is to blame for NVIDIA's inability to produce drivers? I would say it's NVIDIA that's to blame here. I've had so many NVIDIA cards fail on me: I witnessed a friend's NVIDIA card go up in flames, literally, then my own NVIDIA card did the same thing! Then, I had an older NVIDIA GeForce 4 Ti card that died with the classic BGA failure, then I had this latest failure: another NVIDIA card. That's four NVIDIA cards, three of which were mine. So out of all the NVIDIA cards I've ever had (about 5), only two remain. Now, I've had my share of ATI cards (roughly 5) and not a single one has ever failed. Not one.

Sorry NVIDIA, but I'm afraid I must buy ATI cards from now on. Sure, NVIDIA's drivers are more polished, and sometimes NVIDIA wins in terms of performance, but the cards rarely last very long. I would urge anyone who is thinking of purchasing an NVIDIA card to think twice and consider the ATI alternative, and think of which card you'd most likely have to bake. Now, of course, if you like baking, NVIDIA is your friend. :)