Acer Parallel Scanner

I am running Windows XP Professional, on a new machine(1Ghz CPU, 512MB memory, 40Gb Maxtor HD)I’ve installed and reinstalled, manually and automaticly an Acer parallel port scanner model 620P. Everything says that it is “working properly”, however when trying to use it I receive the error message “scanner can not be found”. I’ve considered purchasing a new scanner, but this one works so well and has the best resolutions, including ‘user defined’. Any ideas would be greatly appriciated!