chc.4875E02D9FB21EE389F73B8D1702B320485DF8CE.1

It contains the preferences for the Help Client and the downloaded manuals for CS5. The reason why it's on the C drive is because it's a user preference thing so it goes in your Users folder together with other things like your preferences for Photoshop and the like.

You can lower the size of this folder by opening the Help Client (it's in the Adobe Help folder together with the rest of your CS5 applications or by choosing Help->Photoshop Help or whatever program you're using) and then going to Edit->Preferences->Download Preferences and deselecting the applications for which you want the Help Client to download the help files. After you've done that, go to the Local Content section and delete the help files for those applications.

You'll still be able to use the help files for those programs, it's just that you'll have to be connected to the internet to be able to do that.

I know this is a really old thread, but this is worth mentioning.  Those files he's referring to get saved into not just the User's folder, but into the roaming part of the user's folder.  The idea behind a roaming profile is that when a user logs off, the profile gets copied to a server and then when the user logs into any other PC on the network, that profile gets copied to the new PC.  Pretty cool for when a PC burns up and the user needs to get back to work quickly.  Settings, shortcuts, etc. follow the user to the new PC.  There is also a non-roaming part of the user's profile that sticks to the user only on that PC.  Roaming profiles work great until some software manufacturer thinks it appropriate to save a gig of help file data per user on the file servers.  Developers:  please stop using %appdata%.  Use %localappdata% if that data isn't mission critical to the user.