I decided to play with using my iPhone to give a data connection to a fresh Windows7 install (on my HP Mini 2133, though that shouldn't matter). The following are some notes about how to get it to work and what exactly it does.
First off, be aware that if you use AT&T (as I do) that tethering isn't available to you by default. With Firmware 3.0 they made it very easy to install by using a mobileconfig profile. However I think in 3.1.x (I'm still on 3.0) they locked it out. From what I have read you can re-enable it with a mobileconfig after jailbreaking your iPhone. The jailbreak I know is reported to work with is blackra1n, but who knows what other jailbreak methods may work. Either way, I'm not supporting your jailbreaking issues. But if you've gone there ... (or are using a non-US iPhone that gives you tethering) ... this may be of use.
NOTES:
1) You can tether with USB or with Bluetooth.
2) If you have a fast 3G network, tether with USB, Bluetooth seems to max out around 768Kbs to 1Mbs ... whereas USB is giving me over 3Mbs right now. Uploads on both were the same.
3) If you tether your PC will be getting data from the cellular network EVEN if the iPhone has a working WiFi connection. This is kinda sucky but no way around it using the built-in tethering method, at least so far.
Ok, those notes out of the way ... this is what I needed to make it work:
* Windows 7 fresh install
* iTunes 9.0.2.25 (earlier iTunes will work ... in fact iTunes itself isn't necessary if you can find the Apple mobile device drivers package separately ... but iTunes will bundle it). This is because Win7 doesn't have the USB drivers for the iPhone built-in. You can do USB mass storage without it but not the data tethering. Just grab it from itunes.com.
NOTE: That SHOULD be all you need if you want to USB tether. I'm not 100% sure on that though since I also did the next step before testing.
* Windows Mobile Device Center ... this is a fairly new mobile device driver suite from Microsoft that replaces the old ActiveSync stuff. I used it to get updated Bluetooth connectivity on my Win7 laptop. You can get if from http://www.microsoft.com/windowsmobile/en-us/downloads/microsoft/device-center-download.mspx
I'm not really sure it was necessary since things still didn't work at that point. I found a post about the problem I was having at this page: http://www.conetrix.com/Blog/post/iPhone-Tethering-Cannot-Install-Driver-for-Bluetooth-Peripheral-Device.aspx
The summary of that post is:
* Pair with your iPhone using "Add a Bluetooth Device" in Win7
* Right-click the connected iPhone in "Control Panel -> Hardware & Sound -> Devices and Printers" and select "Properties"
* Go to the "Services" tab
* Uncheck "Wireless IAP"
* "Apply" or "OK"
Then from that point, to connect to the iPhone for tethering, right-click the iPhone in "Devices and Printers" again and use "Connect Using" and click on "Access Point".
So ... the results of all of this? Yeah this may not be worth it for the average user BUT for someone reliant on data while travelling it may just save your butt:
* USB tethering now works. This is the preferred method since it is both easier to hook up (just plug the cable in) AND supports better download speeds as well as charging your phone.
* Bluetooth tethering now works. Forgot your cable? Just need a quick connection and don't need a lot of speed? Just don't want to rifle through your bags? Great. You're covered.
* Remember: all your data is coming from the cell network. I would like it if it would tether the wifi on the phone, just so you could keep a single connection while roaming the airport (letting your phone switch networks at will while the laptop just plays dumb) but ... it doesn't. So if you're not on an unlimited plan you will want to be careful. And if you can't get a 3G signal be prepared for a slow time. But SOME data is better than none.
NOTE: the previous paragraph is a very sad note when you're near one of those free AT&T wifi spots like a Starbucks. It sure would be nice to use tethering in those spots where you get free iPhone WiFi but not free WiFi on your laptop.
