Linked: How To Upgrade VMware ESXi 3.5 To 4.1 Update 1 (Free Version)
One more great guide from the guys at TheHowToForge!
A step by step instruction on how to use the Host Update Utility from VMware.
http://www.howtoforge.com/how-to-upgrade-vmware-esxi-3.5-to-4.1-update-1-free-version
Categorised as: Linked, VMware