"Nowadays all the motherboard support 'bidirectional' parallel ports."

But there's usually a BIOS option to enable it - make sure your BIOS is actually set to enable EPP mode.

"Run the PC in DOS mode..."

Yes, such things were easy in DOS - you could "peek" and "poke" absolute hardware port addresses to your heart's content.
But in Windows - especially the latest versions - it's not so simple. :-(
Win32 doesn't want you to talk direct to the hardware - in fact both Borland & Microsoft C++ compilers no longer suppor inp etc. :-(
Sometimes windows might humour you, and let you think that you're talking direct to hardware, and Win9x is more "relaxed" about it than NT - but they all really want you to go through proper drivers - and that's the only really reliable way.
There was some discussion about this a while back, and I made the above comment then, so a search for "humour" (British spelling) might find it!

The links given so far include references for drivers which do give you access to the port registers.