In general users don't really know how a program works. So whenever a user encounter a crash or other error he will describe it from his own view which is often missleading or wrong

The user is not to blame, but I want to gather as much data as possible when an error occured and want to make it as easy as possible to let the user send this error data to the developer. Currently I write a log file, give the possibiltiy to make screenshots and have some other analysing tools, the problem is, that once a user restarts the game, the log file will be cleared, the screenshots overwritten and all analysing data are gone.

My basic idea is to catch any exception (btw. C++), and then try to pack all data collected so far (screenshots+logfile+on-the-fly analysing data+last save game) and write it to a zip file with an unique timestamp. What do you think , will it work ? Are there better ways to do it, easier ?
What about the players, will they reject to send you data they can't inspect themself (trusting problem) ?
Is it overkill, because most players aren't interested to send you any data, even a small note about a bug ?

An easier method would be to create an error sub-directory and copy all relevant data to it in mostly clear text (logfile atleast), the player could choose which file to send himself.

Currently I write a log file, give the possibiltiy to make screenshots and have some other analysing tools, the problem is, that once a user restarts the game, the log file will be cleared, the screenshots overwritten and all analysing data are gone.
[/quote]
You should change this anyway. Overwriting the logs every startup is something you'll likely regret someday even if it is just you developing the program. You'll have an important log entry you meant to investigate, and you'll accidentally start the program and clobber it.

As for getting the users to upload them, you'll have to just hope. Showing the user what you're going to upload may help increase the response rate. The main thing to ensure is that you're not capturing sensitive data in the logs, and you're not recording where the logs come from.

Most users would expect to be anonymous. For example, if you did a memory dump during a crash and your game includes a login section, you could accidentally capture the username/password in the dump. If this is sent unencrypted you could be exposing the user to any malicious individuals sharing the network.

You should change this anyway. Overwriting the logs every startup is something you'll likely regret someday even if it is just you developing the program. You'll have an important log entry you meant to investigate, and you'll accidentally start the program and clobber it.

Yes, happens all the time I think I will use some kind of round robin logs or writing unique logs and cleaning them up frequently.

You might want to consider using an existing error reporting library like breakpad or, if you use MSVC, you could give crashrpt a try.

Hmmm... crashrpt looks very promising, I will give it a try. Thx

what about writing a minidump ?