I have the same system as you [WinXP Home SP2] and an HP 7300 pluse a Canon SD 550 and now, a Canon SD 700 IS digital camera. So weird you wrote this just now, and I happened to spot it on my Google alert bubble, because I just spent three hours this morning doing the same thing as you -- installing and reinstalling, and getting the message "cannot detect camera." When I installed the software for the SD 550 over a year ago, the software functioned just fine . .. and now neither camera works. I spent over an hour with the Canon technician just this morning who went into my registry files and everything, and we still couldn't get it to work -- he told me he thought my hardware [emachines PC] or the Windows software was corrupted. It's so frustrating because it worked just fine before . . . one thing he did say [and we tried, altho I wasn't successful ]was to UNPLUG the HP printer, and remove or disable the printer device from your hardware "Devices" before reinstalling the camera software, because the scanning function of the printer tends to interfere with the camera software. Then after you've reinstalled that, replug in the printer. Maybe this method will work for you, good luck!