I had to feed my current Windows 7 32bit installation the XP/Vista driver version for our old HP 5000. Works decent.
Our original HP DesignJet plotter was orphaned under Windows XP back in the day. We didn't notice it initially because we had dual installs of AutoCAD 14 and 2000i. Plotting from v14 used its own AutoCAD drivers internally and we never noticed the loss of drivers until we tried plotting with 2000i which used Windows system drivers. I thought the unit was a HP 600 mono, but it was the original DesignJet. I found and bought some third party driver which rasterized the vector graphics, but we ended up trashing it for an OCE.
I'd try Mike's trick with the 1050 drivers.