You haven't said which OS you are using, but judging from the screenshots, you are using Vista. As I don't have Vista, the instructions below are for XP, so you may have to change them to suit your needs.
To make things easier, ensure that you are logging into both machines with the same username and password - this makes it easier to access the files remotely.
On PC 1, go to Network Connections in Control Panel and right click your Wireless Connection and click Properties. On the dialog box that opens, scroll down the list to Internet Protocol and click on Properties.
Click the option to manually use an IP address. Unless you have already manually assigned IP addresses to other network cards or devices, use 192.168.0.1 with a subnet mask of 255.255.255.0 Leave the default gateway and DNS servers sections empty. Click OK twice, and you should be back to the Network Connections window.
Repeat the process on PC 2, this time assign an IP address of 192.168.0.2 with a subnet mask of 255.255.255.0
Now back to PC 1: Open the Wireless Configuration program and click on the configuration tab. Network mode should be set to ad-hoc. Enter a Network SSID - anything will do here - it's the name that your network will be known as.
Tick the Enable Encryption box and select the strongest key that you can. For 802.11g this should be WPA2 - PSK (Pre-Shared Key). Type in a key in the appropriate textbox. To save you the hassle of creating a key yourself, you can use this page to generate one for you:
Create WPA Key for your Wireless Network Router
Make a note of the key, because you'll need it later on.
The next step will depend on your wireless card drivers. You may either need to repeat the exact same steps on PC 2 and manually set up the ad-hoc network with the same SSID and key, or you will have to scan for available networks.
If you have to scan for the network, you should be able to see the SSID you entered previously on PC 1. Double click and you should prompted for the WPA key. Once the two computers can see each other and they are both connected you should be able to browse shared folders. To heck if the PC's are really connected, open a command prompt (Start - Run - type cmd - hit enter) and try to ping the other machine with the following command:
ping 192.168.0.x
where x is the number of the other machine.
If you can successfully ping the other machine, then you are ready to start sharing files. Open Windows Explorer and locate the folder that you want to share. Right click the folder and go to Sharing & Security. When the dialog box opens, tick the option to share the folder and give it a share name. Click ok.
On the other PC, go to Start - Run and type \\192.168.0.x (where x is the number of the other machine). A new window should open and you'll be able to see the shared folders on the other computer.
If you still can't see or connect to the other computer, check for the following problems:
1) Windows firewall/ other firewall product: Has your firewall been configured to allow access?
2) Are both wireless cards the same? Do they use the same standard - 802.11a, b, g, or n?
3) If it still doesn't work, then try allowing Windows to manage your wireless connections. Delete any preferred networks, and start again.
4) Are there any other wireless devices being picked up when you scan for devices? What channels are they using? Try using a free channel to minimise interference.
Connecting 2 PCs via wireless LAN cards.Help :) 
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