It is really quite easy to modify your Path Selection Plugin on VMware ESX using the vSphere PowerCLI which is very useful if you have to modify several hosts. In the below example I am just connecting to a single ESX 5.0 host but you can connect to a vSphere server instead.
1. Connect to the ESX server (Connect-VIServer 10.25.62.65)
2. Check your current PSP (Get-ScsiLun)
3. Change PSP to RoundRobin, MostRecentlyUsed or Fixed (Get-ScsiLun Set_ScsiLun -MultipathPolicy RoundRobin)
If you are interested in what policy to use there is a great article by one of my co-workers about it at