I booted the eBox from the standard option in the boot menu: Boot CE/PC (local nk.bin with /L:1024x768x32)
Next I made a wireless connection from the eBox to my home wireless router by clicking its SSID from the list and (in my case) entering its AES/WPA2-PSK key. My router is configured as DHCP server for known MAC addresses so I had to add the eBox's MAC address to the allow list of my router.
In case you have a long Wi-Fi security key you can put it on a USB memory stick. It will appear under "\USB Storage" in the eBox's filesystem.
After the connection has been made, use ipconfig to check if a proper IP address was assigned.
Next, follow the steps mentioned in Part 6 of the eBox-2300 Windows Embedded CE 6.0 Jump Start Guide
Note: To get Visual Studio 2005 (Express) working on Vista, both VS2005 (Express) SP1 and Visual Studio 2005 Service Pack 1 Update for Windows Vista must be installed
I noticed that after installing the eBox SDK the "eBox2300_WinCE600_SDK x86 Device" didn't show up in the list of target devices in Visual Studio. Renaming my C:\Users\