1. Although your machine may be running 32-bit Windows Vista, chances are that if the machine runs a dual-core processor, which means it can run 64-bit Windows Professional. Most of the graphics, networks, and sound drivers already come with Windows 7, so there usually isn't a need to download extra drivers. Windows 7 should install right out of the box.
2. If you're burning a copy of Windows 7, you may encounter issues about "Required cd/dvd drive device driver is missing". If you observe this case, chances are likely the DVD you burned actually has problems, especially if you were using a copy that hadn't been used for awhile. Originally you may be led to think that there are some driver incompatibility issues with the 64-bit Windows 7 version, but try to reburn the DVD and see if the install works.
3. The touchpad can be replaced, but you have to buy one that comes with the laptop casing too. Since most of the casing + touchpads parts are sold off Ebay for $30+, it may easier to simply attach a USB-mouse instead. The picture below shows an example of the touchpad + upper casing:
4. There are web sites that sell spare keyboard keys (i.e. laptopkey.com), but buying one part can easily cost $8 and you can usually buy the entire keyboard replacement for $12. The HP service manual for replacing the keyboard is fairly straightforward, but there are a few key things to know. In the case of the C700, there were 3 screws at the bottom of the laptop, each with a keyboard icon at the bottom. One of these screws was obscured by the memory lid, so you may have to remove the lid first.
Second, there is the Zero-Insertion Force (ZIF) connector that attaches to the keyboard and laptop. What this usually means is that the sides of the connector need to be pushed out.
You should avoid pulling the ribbon cable out until the connector is released. The picture below shows one example of how the ZIF connector is pushed out. You can usually use your fingers and push the connector out slightly before inserting the ribbon cable. You should push down on the sides to fasten the ribbon cable securely.
Keep in mind that you should verify that all keys work. If the connector is not fully fastened, you may find some keys do not respond. You can try to boot up the computer with the keyboard installed, but be careful if any components are exposed.
5. Finally, if you need to replace any keys, you first have to figure out how the keyboard mechanism works.. There are a bunch of YouTube demos for replacing the keys in HP laptops, but none of the videos I found pointed out that it's easier to attach one of the plastic hinges to the key, and the other smaller plastic hinge to the laptop. If you were to setup the hinges on the laptop first, the plastic hinges should move up and down if you were to apply pressure to them, supplementing the spring-like action in the button.
Once you figure out the right way to place them, take the large hinge and attach it to the key before attaching the other part. For this keyboard, I couldn't just put the key over the two plastic hinges since the pressure of the keys would cause both plastic to be pushed down without snapping into place. You have to be careful with this part since the plastic hooks can break, so avoid trying to force the keys to attach to the plastic hinges.