I tried to install fdm 3.8 and after choosing path destination it ended with it http://imgur.com/0iqRx
fdm installer seems to be agressive into registery or dirty coding.

win 7 64bits
installer took from http://files.freedownloadmanager.org/fdminst.exe

You should not play with your system if you don't understand good enough what you really do. And you should inform the forum about your non-standard actions or settings.
It was many times explained here how to properly install software in Windows Vista and newer systems, so it isn't difficult to find those explanations, if someone really want to. Now you can do as follows:
- turn on UAC (User Account Control);
- change settings of your antivirus or similar software;
- run all installers as Administrator.

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Andrzej P. Wozniak
FDM user and forum moderator