Ubuntu comes with several command line tools which might help you detect more hardware than the Hardware Manager.
lshw lists all hardware.
lshw -short provides a short hardware summary.
Use cat /proc/cpuinfo for a crude, but quick way to display your processor information.
lspci lists connected PCI cards.
lsusb lists connected USB devices.
cat /proc/net/dev lists all the network interfaces. Alternatively, try lshw -class network.
cat /proc/ioports lists communication ports and adresses
cat /proc/iomem shows the memory map and reserved zones.
cat /proc/interrupts lists the interruption assignments.
cat /proc/dma lists the Direct Memory Accessess
lsmod lists the modules loaded by the kernel, and helpt to identify the hardware configured
Ryan's Linux Inventory Aggregator is a Perl script that returns a nicely formatted, short hardware summary, including which drivers are used.