Before we get into the specifics, it would be interesting to know why you have a 64-bit operating system, and if it is a new system why Vista and not Windows 7.
The cheapest, probably most effective way of solving your problem that would allow you to keep your PC and all your peripherals is to install Windows Vista 32-bit (a copy of Vista comes with both 32-bit and 64-bit ready to install). Here's why.
You don't need to understand what 64-bit and 32-bit mean other than in these simple terms; 64-bit allows your PC to make use of far more memory (RAM) than 32bit. This is only useful however, if an application is developed to use the additional memory in the first place; and many aren't. Your applications will still work (in a compatibility mode) but you'll see none of the benefit associated with 64-bit architecture.
Unless you play state of the art games, photo / video editing or some other special software then a 64-bit operating system (O/S) can do more harm than good. As I say above most of your applications will work, the real issue then is with your 'drivers'. Drivers are the software used to help your PC talk to your devices and peripherals such as printers. Many companies are slow to support 64-bit as it is an additional expense to code and test the device. So switching to 32-bit should solve your compatibility problems whilst not impacting performance.
The big picture is that at some point the industry will reach a ceiling with 32bit systems as applications become more robust and memory intensive. Microsoft intend at some point to phase out 32bit, and are in fact already working to introduce 128bit architecture, but we are a good few years away from that right now. So from what I can glean by your post, 32bit Vista is for you, and will most likely fix your compatibility woes. You can read more on the trade-off between 64bit and 32bit here: http://windows.microsoft.com/en-US/windows-vista/32-bit-and-64-bit-Windows-frequently-asked-questions ; or Google 32bit vs 64bit for a wealth of articles on the subject.
Finally, if you are adamant that you need to stick with 64-bit, it may be worth upgrading to Windows 7. You can make your own mind on cost vs features but in my experience the driver support is generally better. (For what it's worth I run 64 bit windows 7 and have many devices linked to it). Seeing as you should already have a paid up version of Vista 32bit (you should have got an install disk with your PC, or call HP Support) then, for the sake of saving your pennies, simply reinstall Vista 32bit. It is worth noting, before you decide that unlike Vista (where one licensed copy comes with both 64 and 32bit versions), with Windows 7 you will have to chose.
If you do decide to take my advice, as with any upgrade be sure to back-up your personal files and check out some prior CNET posts on how to efficiently reinstall your operating system.