Hi! Windows 7 started? What are tech specs of your pc/laptop/netbook?

If you have dual core CPU and at least 2gb of RAM (which i doubt, windows 7 starter is for rather low-end computers) i would recommend you virtual machine with linux on it (I use VirtualBox with old Ubuntu 10.04 installed, it has good old Gnome 2 gui and Maemo 5 SDK can be installed on it flawlessly).

If your computer has worse performance, I would recommend using Ubuntu live from USB or, maybe better solution for you if you have > 10 gb free disk space on your HDD, WUBI.

You might as well use Windows, but if you plan to write software for N900/N9, I would go for linux anyway (unless you plan to do only really simple or Qt stuff, then you can just install Qt Creator.

As for coding, in my days, one should typically begin with basic C++ knowledge, http://www.cplusplus.com/doc/tutorial/ may be good for beginner (there is pdf version available for download, you may want to download and print it to give your computer a break, Qt Creator is heavy anyway), but maybe you would prefer Python - it may be easier, because you can install Python in Widows 7, code and test there, then just transfer script (what you write in Python is not really a standalone executable program, it's script which is run using Python parser and libraries) to N9/N900/N950 and it should still work.

Summary: use Ubuntu on virtual machine or with WUBI if you are not afraid of Linux, but if you are ("only used a few commands in xterm" - that suggests you are not familiar with Linux), you may just install Qt Creator for Windows and practice C++ there or install Python for Windows and practice there.