There shouldn't be any issues provided that the other charger is able to output at 5V and not exceeding 1A. Most HTC phones uses mini USB (or mini USB EXT) standard connectors. Recent newer HTC phones uses micro USB standard connectors. So most chargers that has one of these connectors at the other end (including car chargers) will be able to charge your phone.

Just be aware of the charger's output specifications. If it uses a standard USB connector, it should be 5V (USB standard) while the ampere should not exceed 1A. It can charge even with 500mA but it's gonna be slow so anything above 850mA to 1A is good enough.