Almost always when I try to print anything, XP informs me that "the handle is invalid". First this started to occur after XP had been up too long, about two hours or so, and later it became a problem that wouldn't get fixed even if PC got rebooted.
I learned that it has something to do with print spool service. Restarting this service helps once in a while, but usually it requires something more drastic like reinstalling printer drivers.

I've also read that having some HP printer drivers on computer may cause this with other printers. However, I do not have any such drivers. But: I am using HP's PC, and I've found some HP software on my hard disk installed by default. I guess it could therefore be possible that there were some hidden HP drivers on the PC, but I do not know where to look. And in any case I find it doubtful that any of such drivers were active. But you newer know...

So, if anyone can help me, I'd appreciate it.

I am using: XP Home SP1, Canon S500 and the latest drivers, and (I'm telling this because McAfee has caused some similar problems) Norton Internet Security (AV is 2004, firewall 2003), which didn't cause any problems on my previous PC and with the current printer.