Can I lock (hardware id) to a single PC my application when it's running in Trial Mode?

Sorry but applications in Trial Mode cannot be locked to a specific computer. If you specify a 15 days trial period for your application, it will run during 15 days on ANY computer.

If you want to limit time your application and also lock it to specific machines (and not locked to other machines), you have to create licenses for your application.

You can create a license (with 15 days restriction, for example) and set the "HardwareID" field in the license to restrict the license to a specific machine, so, it can only be used on a machine.

If you create a license, leaving the "HardwareID" field as blank, the license will run on ANY computer.

Summing up, if you want to limit time your application and restrict the execution in some machines, you have to create licenses with expiration (and specifying the HardwareID for those licenses that you want to lock to a specific machine)