May I note that automatically starting the download without the user's confirmation is a very bad thing to do...
For all you know the user is downloading the file from an OS he isn't going to install it on. Also, with such auto-downloading the user might get the impression that the file will work on every OS/Computer, again not a good thing...[*]
And, MSN Messenger comes in different languages. Again the same story, it is well possible that the user doesn't want to download the version you autpmatically provide.
Always let the user confirm and always have a manual overwrite option so the user can change his preferences.
The question is also: why do you want to provide a download of your own? Just link to
http://messenger.msn.com/ or the correct
http://microsoft.com/downloads/ page. This is also good in the sense that there might be more info on those pages which the user should read/know...
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*: Also know that MS provides installers of MSN Messenger which work on all Windows versions. You reconize these by their slightly larger downloadsize (because they include one installer for Win9x and one for Win NT) and by their name...
versions provided by
http://messenger.msn.com/
blahblah
95.exe => Installer specifically for Win95
blahblah
NT.exe => Installer specifically for Win2K (and in previous major versions also for NT4)
blahblah
9X.exe => Installer specifically for WinME, 98
blahblah.exe => Installer specifically for WinXP or for all OS's (depends on what build it is)
versions provided by
http://microsoft.com/downloads/
blahblah.exe => Installer for all OS's
on both sites it could happen that you come across:
blahblah
DL.exe => Installer without InstMsi.exe
InstMsi.exe is the Windows Installer needed to install those MSI packages. It automatically checks/updates/whatever the Windows Installer.
eg:
MSN Messenger 7.5.0299
http://www.microsoft.com/downloads/details.aspx?F...-977a-5d49e5a4ecda
MSN Messenger 7.0.0813
http://www.microsoft.com/downloads/details.aspx?F...-bb0b-efb7668b4ff7
MSN Messenger 7.0.0777
http://www.microsoft.com/downloads/details.aspx?F...-b6ee-bf0ec49f393a
MSN Messenger 6.2.0208
http://www.microsoft.com/downloads/details.aspx?F...-9f05-1ff3c799bb10
MSN Messenger 5.0.0575 (win95 only)
http://www.microsoft.com/downloads/details.aspx?F...-b24a-86edffcdba02
MSN Messenger 5.0.0575 (win2k/NT4 only)
http://www.microsoft.com/downloads/details.aspx?F...-866b-e206a84f0df8
etc...
To know exactly which file is for which OS, you need to open the archive (as that is what those exe actually are) with winzip or winrar or the likes, and look for InstMsiA.exe and InstMsiW.exe. A is the one for 9x and the likes, W for the higher OS's. (A = ascii version, W = supports unicode)
If you ever come across a file with extension .msi, then it sure is not an official and/or public released version as it doesn't contain any installers and MS will never release such a MSN Messenger package on its own.
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