You need to go into wireless settings then USB settings and select massstorage go back to your desk top plug in your phone it should show up a android robolt and a box that says USB storage press If you do not press this it will not work
now windows will look in the Kies folder and find the drivers and instal them and it will open two drives just like a USB stick the folders were your pics are are in DCIM
Now if windows does not see the phone then you need to open your device manager and you will see yellow !
Which version of Windows are you using? By default the S2 should be picked up as an MTP device if you don't have Kies installed as Windows XP SP2 and beyond support MTP natively. The Kies Air application is separate as it's for remotely controlling the phone or something (haven't tried it), the main Kies application is around an 80MB download from the Samsung site. It should show items like contacts, pictures, videos and prompt you to connect the phone over USB or wifi, once connected it should load the drivers and allow you transfer data.
Right if your not wanting to use wifi then the only way is your windows 7 machine as explaned it uses the MTP protacl which was first used on windows Vista. Now manufactures don't have to give support for XP any more some still do mass storage uses the PDA type of accses