It was only a matter of time, after I got the Bochs PC emulator working on N900, I just had to try how slow Windows NT 4.0 would be inside it I'll post further details of how exactly I did it later, but for now, here it is:
I've received some questions and would like to post the answers right here in case others are wondering the same things about the N900:
Yes, the memory on the device is partitioned so that you have around 1.5GB or so for applications, and the rest for data (images, videos, music, maps, software you use with DOSBox, etc.)
To install Dosbox you have to add one or all of the extras repositories in your device App manager: extras, extras-devel, extras-testing. More instructions about that are available at: https://wiki.maemo.org/Extras
I did some tweaking and uploaded a faster Windows 3.11 running on N900-video to Youtube. The most important changes were setting frameskip=6 in dosbox preferences and installing of S3 video drivers in Windows, which had a huge difference in speed. I would have liked to test how well it would have worked with a Bluetooth mouse and keyboard, but I still don't have any to try it with.