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.

okey dude this was the same problem i faced and i was piss off...

then i searched and found Libusb win32 or 64 depends on your installed operationg system...

and secondly i was confeusing for me when they wrote in the flash instruction that not to restart...

yes u don't have to restart and both emm and firmware will not start automatically even if u type -R in the comand line...

the solution for your question is download lib usb for eithe windows xp or 7 there is the link

http://www.libusb.org/

all u have to do is install the driver through libusb...

let me know it u wana know any thing else...

u need to run cmd as administrator in windows 7.
just right click on cmd and select Run as Administrator

much easier would be make a linux bootable disk and login and flash from there... it is just pain to get it work in windows...

oh ya one more thing don't connect the n900 untill it says device not found press enter to rest or sonthing like that...

when it show you that command then keep on holding U and plug in the usb...

I believe the flashing instructions also suggested that you can install XP-Mode. Of course, the host need to recognize the USB connection first.

Also, you'd not want to use a USB hub for reflashing, which I'm sure you've already acknowledged that. Try other USB port when you're still get stuck in this.