Check the documentation on the Switch. some of the smaller (un managed) HP switches carry caviots about connecting devices that are hard coded for 100 full duplex. The gist of these notes are that if the device you are connecting is set 100 full the switch may not correctly auto negotiate its connection.
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Here is an excerpt from the 408 switch manual:
Connecting to devices with a fixed full-duplex configuration.
The Switch 408 ports are set to auto-negotiate the link
characteristics. That is, when connecting to attached devices, the
switch will operate in one of two ways to determine the link speed
and the communication mode (half duplex or full duplex):
? if the connected device is also set to auto negotiate, the
switch will automatically negotiate both link speed and
communication mode
? if the connected device has a fixed configuration, for example
(100 Mbps, and half or full duplex), the switch will automatically
sense the link speed, but will default to a communication
mode of half duplex
Because the Switch 408 behaves in this way (in compliance with
the IEEE 802.3u standard), if a device connected to the switch
has a fixed configuration at full duplex, the device will not
connect correctly to the Switch 408. The result will be high error
rates and high collision rates, and very inefficient communications
between the switch and the device.
Make sure that all devices connected to the Switch 408 are
configured to auto negotiate, or are configured to connect at half
duplex (all hubs are configured this way, for example).
