What kind of electrum did you download? I guess you download the standalone am I right?
You must download the windows installer and install it so that it will create a folder in program files(x86) and wallet data in %appdata%/roaming.
If you use the standalone it extracts the electrum files in %temp% folder every time you run it while the windows installer will create a shortcut and extract files in the program files folder.
For the portable version, it will extract the files in the same directory or folder.
Also, if you want to open your old wallet you must use the open button or use the new/restore button from electrum.
Click open and then locate your old wallet.dat now it should work.