I would suggest 2 possibles if using windows...
Xp in a vm...
Or win 7 in a vm...
Or usb stick (possibly...I personally have never done it via a usb install of xp or 7...)
Or if you just happen to have 7 on a system ...it will work...
On 10 it should work ...though I haven't tried 10...
But with 7 and 10 both ...odds are you will need a couple of drivers installed so everything is recognized properly...
They should be available in the wayback machine save...with the firmware downloads...

Yeah...just plugging into 10 and expecting it to just accept the n900 and the pc suite properly...is unlikely...without those necessary drivers...
And even then...with 10...there may be other issues ...
I have not bothered attempting reflashing or pc suite with 10...yet....so I do not know all the probs possible...
This winter I may fiddle with 10 and firmware and pc suite.

Also...you could grab an old iso of ubuntu...that and the linux flasher does very well...ffffsomethingsomething (I can never remember the name of it)
I do not know if the very latest ubuntu handles the li nux flasher well or not....