To change the Wireless Password:
- Power on the MiFi
- Navigate to http://mifi.admin
- Sign into the MiFi admin console using the admin password
- Click the WiFi tab
- Change your Security password type to whichever option you prefer
- Click Apply
Older computers can sometimes be updated to support WPA2 wireless passwords. If you haven't already tried then it might be worth looking into. Also, if your wireless card is causing the connection issue it might be time to look into replacing it with a better one.
Let us know if you need more help or suggestions.