Even though your original post is a year old... I had the same issue. I downloaded the win7 x64 driver package 9.1.0.328,A01 and it failed with the same problem. (The weird thing is I have another Inspiron 620 running win7 x64 and the current driver installed, originally from Dell,  is version 9.1.0.328?) So, I tried the other available win7 x64 package, 9.2.0.517,A02. Again, failed with the same "The installer can not run on this platform." I decided to try and manually install the driver instead of using the installer. Go to - control panel/hardware and sound/device manager and right click on this adapter in "network adapters" Click on "update driver software," browse to the proper directory on C: that was created from the package extraction and click "ok."  I was able to get my dell 1502 working this way. I deleted the complete directory that was created from package 9.1.0.328. I ended up with ver 9.2.0.517... only because it was the second package that I extracted. I assume that 9.1.0.328 would've probably worked this way too.
Tried pulling this card out of a new Dell Vostro 260 (where it's not needed) and putting it into a Dell Optiplex 360 with Windows 7 x64.  When attempting to install the driver the setup.exe gives the message: "The installer can not run on this platform."  I've tried verifying that I'm selecting the Win7 x64 option for download but still no luck.  The file info is Atheros-Driver 5/26/2011 - Version  9.1.0.328, A01. Is this card not compatible with older Core 2 Duo hardware, and require an i3 + chip perhaps?
Dell Wireless 1502 (802.11 b/g/n) WLAN half mini-Card