It might be a good idea to make a clean install, but a word of caution is in order.
Large OEM manufacturers often use proprietary hardware, especially on laptops and special form-factor desktops. I am not sure about the HP slim-line, but as an example, I recently got a new Sony laptop and decided to do a clean install. Once I've installed Windows, I needed to download Sony drivers for almost all the hardware on my laptop. Sure, these drivers are indeed available either from Sony's website, or from the restore disks. The restore disks however use a certain Sony app to manage the restores, so I had to install that as well, which in turn required some other Sony stuff. It's a bit of work. As an alternative, I have a desktop from Dell which turned out to be a regular desktop, no driver issues at all when I installed Windows 7 instead of Vista which came with it.
So, before you re-install, make those recovery discs and gather all possible information about your hardware, making sure that you know where to get the drivers from in case they are needed.