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Today I installed Visual Studio 2008 SP1 and I accidentially detected that the installer created temporary files on a USB hard drive I just plugged in.

I can imagine what happens if I had unplugged it during the installation...

Why did the installer choose my external USB hard drive over the internal hard drive which is much faster?

Is there anything I can do to prevent something like this? Can it be configured using WSUS?

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up vote 2 down vote accepted

Windows Installer evaluates the drive with the highest amount of available space with the exception of network drives.

Then it generates a GUID as a folder name, which is why you end up with the names of 8ffa4cads222f11af33ae and the like. :)

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I assume you mean an update that needs to be extracted from an archive before being run, and that is presented as a self-extracting archive that unzips itself to a temp folder called something like "dfgkjshdksnvlkdfnvshdf"?

I think it just uses the fixed drive with the highest available space. A USB HD will present itself to Windows - in certain scenarios - as a fixed drive (e.g. you can see it in Disk Management), so that's why it got used.

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are you using vista and using the key for readyboost?

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