Internet service for laptops

I would like to use the internet on my netbook in Japan for little bit over a month. I have few questions regarding that.

I'm not completely sure how the service works. Do I need to have a receiver (no idea what they are called) plugged in my computer? Somewhere in the forum said you can rent that. Like most cellphone companies, are services like these only for 1-2 year contracts?

I prefer Docomo service, and I checked their website, but It left me still confused about the service.

If I plan to use for only about a month, should I be looking for ''prepaid internet service''?

I would be appreciated if anyone can give me some more info regarding internet services by cellphone companies!

Where and when will you need to use it? Are you a resident or temporary visitor?

If you are staying at hotels, note that a lot of hotels offer free internet.

As for wireless services, there are various companies. Here is one with an English website, which offers 1-day passports that require no contracts:
http://www.hotspot.ne.jp/en/servicemenu/1day.html

This one probably cost more then your netbook at around $400, but 150 hours it offers should be plenty for a month. I'm gonna try their less expensive one which only offers 150minutes since I'll only be there for 9 days.

It's a USB 3g modem using the Docomo network that you just plug into your computer.

http://www.bmobile.ne.jp/english/3g.html