Don't worry! It's only stuff...

Update firmware
1. save firmware file in root dir on a TFTP server
2. telnet SWITCH_IP
3. copy tftp flash TFTP_SERVER_IP FLASH_FILE.svi

Kernel 2.6 boot parameter
You need to add
pnpbios=off
vga=0x314
to your boot parameter command line else Evo T20 will hangs during boot process.

Links
http://mowson.org/karl/evo_t20/
http://en.wikipedia.org/wiki/Geode_(processor)
http://www.kazak.ws/evo/
http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareIndex.jsp?lang=en&cc=us&prodNameId=100771&prodTypeId=12454&prodSeriesId=96470&swLang=13&taskId=135&swEnvOID=1056
http://www.baldar.de/pub/Compaq_Evo_T20/
http://www.pug.org/index.php/Thin_Client_evo_T20