This, in my mind, is still one of the better handhelds that HP ever made. It used an Intel XScale 400 MHz processor and came with 64 MB of RAM. Expansion was via an SD slot. Available peripherals included a camera and a GPS unit. The OS was Windows Mobile 2003. It also had built-in Wi-Fi and Bluetooth connectivity.
Optimized for multimedia, the 4155 excelled at playing audio and video. The charging cradle could hold a second battery, which could be charged along with the main unit.