T-Mobile HTC Desire with Virgin Media?

Did you mean you want to access your phone with virgin sim?
Yes means,Make sure your HTC Desire phone is unlocked.If it's locked means,you will need to unlock it.You can unlock your phone by network unlock code.You can get an unlock code from your service provider or else try to buy an unlock code from any one of the online unlocking service provider like Unlock-Zone.com Once unlock your phone,you will be able to use Virgin sim without having any problem.