Hero Online has recently had updates to specifically fix Widescreen issues, (mostly issues on some laptops) and now should work natively on all systems.
Hero is HOR+, and requires no fixes. (except when changing to a resolution below 1024x768. discussed below)
I have tested this game recently at 800x600, 1024x768, and 1280x800.
There is a minor issue however, only resolutions at or above 1024x768 show up in the options. If you would like to set a lower resolution go to your "hero_online" folder and open the "TDH_Launcher.ini" and find the lines "screen_width=" and "screen_height=" and set them to the resolution you would like to use.
I had tested Hero Online a while back at 640x480 (using the above method) and it worked fine, however, it seems now that Hero Online will only ALLOW resolutions at or above 800x600, because anything lower than that and I get a message telling me to change to a "supported" resolution. I will edit this post if I find any more info on lower resolutions.
NOTE: If you set a custom resolution using the .ini file, don't go into the options menu in the launcher. You may still change options in game, but if you select options from the Launcher, before the game starts, the resolution will change back to 1024x768.