DLL-Files Support says:
Getting an error regarding c:\users\<username>\appdata\local\tbhostsupport\TBHostSupport_O.dll missing at Windows startup?
The file TBHostSupport_O.dll is classified as malware by many providers, typically distributed by way of a thirdparty installer or toolbar browser highjacker. It is not recommended that you attempt to reinstall this file on your computer, which is also why we do not offer this file for download.
As far as I can tell, this is a PUP from Conduit. It’s technically not a virus, but it does exhibit plenty of malicious traits, such as browser hijacking, and in general just interfering with the user experience. The industry generally refers to it as a “PUP,” or potentially unwanted program.
To stop this file from being loaded at Windows start, remove the autostart entry.
How to remove the Startup entry:
Win XP, VISTA, 7: Press "Windows"-key + "R" to bring up the "Run" dialogue. In "Run" dialogue type "msconfig" and hit Enter Under the tab "Startup", uncheck any boxes relating to these files.
Win 8: Press CTRL+SHIFT+ESC at the same time to bring up the Task Manager. Under the tab "Start-up", uncheck any boxes relating to these files.
Should you not find any references here to the TBHostSupport_O.dll , try the Microsoft program Sysinternals Autoruns.
Available for free at: http://technet.microsoft.com/en-US/sysinternals/bb963902.aspx