Ouch...no offence, but by getting hold of Voodoo3 you´re barely pushing your specs-problem away for a couple of weeks. With a PII/PIII and Voodoo3 you`ll go through a lot of disappointments in the coming months when you buy new games. Most of them won´t even load properly, and with the games you manage to load you´ll experience A LOT of lagging and other annoying problems.
Other problems with Voodoo3 is that since Nvidia killed off 3dfx there are no updated original drivers. Which means that all you´ll get hold off are 3rd party drivers which can be very unstable.
However, if you for some reason can´t dish out money for a new motherboard, processor, RAM and video card, then you´d might wanna push your system by overclocking, using application accelerators, using tweaked drivers, manage application priorities etc. Some tweaking has a small element of risk, but safe procedures like overclocking is something you definitely should think about.
And for your questions...

Yes, you can have both 810E and Voodoo. And I trust my DxDiag more than I trust an HP-tech - there is no way no 810E has ever had a memory of 11mb.