N900: Windows 64bit (Vista&7) According to
this post, windows driver signing can cause problems. You either need to turn on the loading of unsigned drivers or boot your computer to whole another OS.
There are a few option the resolve these problems :
Option 1 Disabling signed driver detection is done by choosing the option "Boot without checking for signed drivers" (or something similar) in the boot-menu. To display the boot-menu press the "F8" key as soon as the windows boot process starts. The rest of the process is similar to XP.
Option 2 Alternatively you can permanently disable driver checking via command line manager. There are good instructions for windows 7 available
[2]
Option 3 You can use
[3] Microsoft Virtual Pc - Also known as XP Mode.
Enterprise and Pro versions of window 7 come with free windows xp mode, download and install is needed to use though.
1. Connect your phone in update mode. (power off > hold u on phone keyboard > connect usb cable).
2. Wait till windows 7 installs drivers.
3. Start windows virtual pc (xp mode).
4. On the top, you have an option to make the virtual pc get access to your N900, you need to click on USB > N900 (Attach).
5. Wait till it installs drivers.
6. When it's done, proceed with flashing steps.
