Suitable USB device not found, waiting. with Windows 7 Service Pack 1, anyone know how to solve this problem?

Updating or re-flashing the firmware using the Flasher

Note: This method is fully compatible with 32-bit versions of Windows; 64-bit users may encounter problems. There is a workaround that is reported working though at talk.maemo.org

To flash from the Windows (XP, Vista, or 7) command line,

Download and install the latest version of the Flasher.
Download the latest firmware (.bin) file for your region and save it to %ProgramFiles%\maemo\flasher-3.5\ (the default path), or wherever you installed the Flasher.
Ensure the battery is at least half full.
Unplug USB cable if present, and switch off the device.
Run the Flasher from the Start menu
This is an alternate to step 5, if you have already opened the Flasher, ignore this step. Open the Command Prompt (Start then Run or Windows Logo key + R) and type cmd then press Enter. Change the directory to where you installed the Flasher (TIP: Use the TAB key to auto-complete commands and file-names)

cd "%ProgramFiles%\maemo\flasher-3.5"

Hold the u key on the device keyboard and connect the USB cable at the same time. See the Flasher documentation for more information. (TIP: Hold the u key until Windows has successfully installed the driver.)
Run the following command (TIP: Do not include '-R' if you are flashing EMMC as well, see below):

flasher-3.5.exe -F RX-51_2009SE_2.2009.51-1_PR_COMBINED_MR0_ARM.bin -f -R

Replace RX-51_2009SE_2.2009.51-1_PR_COMBINED_MR0_ARM.bin with the firmware you wish to update. (Make sure you have downloaded the actual corresponding file.) The latest PR1.3 official (rootfs) images are listed below:

USA

RX-51_2009SE_20.2010.36-2.002_PR_COMBINED_002_ARM.bin

Middle East and North Africa

RX-51_2009SE_20.2010.36-2.003_PR_COMBINED_003_ARM.bin

India

RX-51_2009SE_20.2010.36-2.004_PR_COMBINED_004_ARM.bin

UK (not the vodafone firmware, but fully compatible with vodafone devices).

There is no seperate UK firmware at this time.

Global

RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM.bin

The flash will take approximately 2-5 minutes after which the N900 will reboot and display the Welcome Screen with Regional settings. After booting, you may use the backup utility to restore your settings.