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!
I run WinXP Home SP2 and have a HP PSC 2353 plus a Canon digicam.
Bothe the HP and Canon worked perfectly for ages then the Scanning function on the HP and the Canon stopped working. The HP error is 'An Error Occurred Communicating with the Scanning Device'; and the Canon's message is 'Cannot detect camera'
I have unistalled and re-installed both lots of software; I have updated to the latest verions; I have deleted the USB devices through the Device Manager. I Have tried different cables and different USB ports (I have some on a PCI card) I have closed all other programs including anti-virus and firewall. No luck with any of that.
I tried going back to the earliest system restore - no luck.
I haen't loaded any new software, only reloaded my anti-virus.
Can anyone suggest what to do.

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