Problems with the student offer download

Ok hope someone can help me.

I downloaded the pre-installation file and got to the point where it was "opening the box" when it gets to the end an error comes up and says "We are unable to create or save news files in the folder in which the application was downloaded. Please check the folder propeties to make sure that you have security permission on the folder to write files and that the folder is not read-only"

Now I went straight into the properties of the "extended setup" folder and unclicked the read-only box... now I pressed ok, and restarted the "open the box" exe. At the end the same error came up... I looked into the properties again and where it says read only, it's not a tick it's a green blob and however many times I unselect it, apply it, ok it for all folders etc, it keeps reselecting itself with this green blob instead of a tick.

I can't seem to find a way round it, and thus I cannot yet install windows7.

Bit more info, the installation is going on a new clean drive, I'm trying to achieve a dual boot from win xp home. My main drive at the moment is D:/ (long story) and I'm hoping after installing 7 with a clean install, I can then transfer my pictures and music etc from D:/ to the new recently formatted C:/

At the moment, I'm waiting for the disc that came with the student offer to see if it that will help solve the installation. Problem.

Any advice welcome. Please help! lol
Heather