LR, this Laserjet 4P question's been answered before: it's part of XP's default driver set, you simply need to start -> printers and faxes -> add a printer -> local printer -> deselect autodetect to speed things up a bit -> select LPT1, etc as appropriate -> Under manufacturer, select HP; under printers, select HP Laserjet 4P -> DON'T click Windows Update or Have disk, simply click Next -> Next (probably). Voila.
Some of the titles may be different, I'm not in front of a PC at the moment.
Driver Detective does nothing that you and Google can't do. "Free download" is a typical conning phrase, and should have alerted you.
But anyway, for most HP printers from the 90's, the drivers are in XP.