So you can download then. You just can't seem to install software. There is a BIG difference in the two.
To change User Account Control Settings:
Bottom left corner, click the 'Start' button (blue circle with Windows logo).
Next type uac in the box and hit enter.
When the window pops up, slide the slider to the bottom, click OK and reboot. Now try to install something. I doubt this is the problem but it's worth a try.
You also need to be logged in as an administrator. Click the 'Start' button and type 'computer management' then hit enter. When the window pops up, click on the arrow beside 'Local users and groups'. Next click on the folder 'Users'. Next right click on your login name and select properties. When the window pops up click the 'Member Of' tab. Verify that 'Administrators' is in the list.