Well I can confirm that I have a Dell PowerEdge T105 running smoothly with ESXi, This system is running from a USB stick thats plugged into the motherboard. No issues!
Spec
Dual Core Opteron 1216 2.4Ghz
2Gb Ram
250Gb SATA Drive
1 Onboard gigabit NIC + 1 3Com 100Mbps NIC
The system at the moment has one VM running Windows Server 2003 Standard RS2, I have yet to install WSUS for some serious performance testing.
I'm novice to ESXi. I guess You mean you installed ESXI from Internal UBS drive. Is that correct?
I am trying to install ESXI on Dell T100 but getting an error: "Unable to find a supported devide to write the image" when trying to install from DVD.
Did you face this issue?
I'm about to attempt the same on an Athlon based T105, with 8Gb of RAM and a 1.5Tb SATA drive.
Any tips on how to install ESX3i to boot from USB?
Nevermind.... I stumbled my way through it... and it works as expected.
Were you able to install on Hard Disk or just using it from USB?
Do you know if there are any risks to run ESXi from USB?
You'll want to use a quality USB 2.0 certified USB flash drive. And regardless of where you run ESXi from (flash drive / hard drive) you should regularly backup your ESXi config in addition to the VMs - http://www.vm-help.com/esx/esx3i/esx_3i_rcli/vicfg-cfgbackup.php.