Ralink usb wireless

It should perhaps also have directed you to http://wiki.wireshark.org/CaptureSetup/WLAN, which says

Windows

Capturing WLAN traffic on Windows depends on WinPcap and on the underlying network adapters and drivers. Unfortunately, most drivers/adapters support neither monitor mode, nor seeing 802.11 headers when capturing, nor capturing non-data frames.

Promiscuous mode can be set; unfortunately, it's often crippled. In this mode many drivers don't supply packets at all, or don't supply packets sent by the host.

If you experience any problems capturing packets on WLANs, try to switch promiscuous mode off. In this case you will have to capture traffic on the host you're interested in.

This is because:

1. WinPcap uses version 5, rather than version 6, of the "NDIS" interface for connecting to the Windows networking stack, and NDIS version 5 doesn't support "native Wi-Fi" and thus doesn't support "monitor mode";
2. even if it did support NDIS version 6, Windows XP doesn't, so you'd have to run Vista or 7 to get that;
3. Microsoft's specifications for Wi-Fi drivers, as I remember, essentially say that promiscuous mode is not allowed to work.

AirPcap devices aren't regular Wi-Fi adapters; they're special devices for passively capturing Wi-Fi traffic, so they don't use the "NDIS" interface, and thus can do things you can't do with WinPcap and regular Wi-Fi adapters.

Other operating systems, such as Linux, and {Free,Net,Open,DragonFly}BSD, don't have those limitations; an RT3070 device might support capturing in monitor mode, depending on the capabilities of the hardware and the driver.

If all you want to do is capture traffic to and from your machine, that should work even on Windows - just turn promiscuous mode off and see whether that works.

(As for USB, if the Wireshark help referred you to, or said something similar to, what http://wiki.wireshark.org/CaptureSetup/USB said, what it's saying is not that you can't capture on USB network adapters - Wireshark doesn't know anything special about USB network adapters, and neither does WinPcap or even the Windows networking stack, so they can't distinguish USB adapters from, for example, PCI adapters - it's saying that you can't capture raw USB traffic at the bus level on Windows the way you can on Linux.)