Hello tormodfoss--
I don't remember the temp folder which I usually access by typing %temp% in
run or typing temp in the Vista Search Box but the error isn't uncommon and
discussion of it is in the Adobe KB here:
Error, "The Temp folder is on a drive that is full..." when installing
Acrobat 8 trial or Adobe Reader 8 (Windows Vista)
http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=333643
Have you disabled UAC (User Accont Control)? Other solutions are also
discussed.
Do one of the following solutions:
Solution 1: Enable User Account Control.
In Control Panels, choose User Accounts.
Click "Turn User Account Control on or off".
Check the box to "Use User Account Control (UAC) to help protect your
computer" and then click OK.
Restart your computer.
Install Adobe Reader 8.
Note: You can turn off User Account Control after you successfully install
Adobe Reader.
Solution 2: Run the installer in XP Compatibility Mode.
Download the Adobe Reader installer from the Adobe website. When you are
prompted to run or save the file, choose save. Save the file to your
desktop.
On the Desktop, right-click the AdbeRdr80_en_US file and then choose
Properties.
Click the Compatibility tab.
Under Compatibility Mode, check Run this program in compatibility mode for:
and choose Windows XP (Service Pack 2) from the drop down list.
Click Apply, then click OK to close the Properties window
Double-click the AdbeRdr80_en_US file and continue with the installation.
Good luck,
CH
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