How to choose a USB to Serial Device that has preloaded drivers on the OS.

Microsoft can't preload a large number of drivers due to the size issue.  Even on a 4.7 GB DVD, there's only so much room.  That's why the automatic driver finder was originally added to XP.  Since then it has become more effective, and since W7 most Microsoft-approved and qualified drivers (WHQL) can be found through automatic lookup and download from Microsoft.

Unfortunately USB to serial interfaces are a niche item so it's unlikely those drivers are preloaded on the DVD.  Further, since every Chinese manufacturer makes their own variant on the basic unit, there won't be a lot of Microsoft-approved and qualified drivers available through automatic lookup.  And it's not uncommon for the driver mini-CDs supplied with devices purchased from fleabay to be infected with viruses.

I'd stick with Belkin, SIIG or Startech and buy them only from a reputable US seller such as Newegg.  It will be more expensive than the bargain basement units from fleabay, but it's also less likely that the driver CD will be infected.  But you'll still need to load the driver from CD, and it's not probable that the driver will be WHQL approved.