The way I understand the situation, your actual problem has been successfully solved, you're just complaining about the difficulty of solving it, right?
To be fair - there are millions and millions of different printers and other devices out there. HP itself produces more printer models that one would think possible. Therefore it is a bit unrealistic to expect, that any operating system (including Windows 7) will contain support (i.e. generic drivers) for all of those devices.
As far as your printer goes - you said it yourself, HP did not have a driver for Windows 7. I do not understand why people think that this is the problem of the OS or Microsoft's fault. When a new OS comes out it is up to device manufacturers to provide drivers. Naturally they do it on their own schedule and most often they don't make this schedule public.
Basically, all of the above should be taken into consideration *before* you decide to upgrade your OS or buy a new computer (which would likely come with a new OS). Will the new OS be compatible with your printer, scanner, and other devices? It's up to you to find this out (it's not hard, just go to the support page of your device and check out available drivers). Then it's up to you to decide whether it's worth to upgrade the OS.
Finally, if you own a mainstream home printer, then most likely the price of a new model is comparable to the price of the new set of ink cartridges. If you have such problem again in the future, you might want to check out the newer printer models - sometimes it makes sense (there may be a special deal at your friendly retailer) to get a newer printer instead of new cartridges.
