WEP or WPA are a general security measured and it does not matter what hardware they work on, they follow the same principles. They all have to match the Wireless Router (source) that is used.
WEP is Not secure, and rather easy to crack.
WPA with good 8 charaters (or more) is secure.
WPA2 (WPA+AES) is even better.
From the weakest to the strongest, Wireless security capacity is.
Switching Off SSID (same has No Security. SSID can be easily sniffed even if it is Off)
MAC Filtering______(Band Aid if nothing else is available, MAC number can be easily Spoofed).
WEP64____(Easy, to "Break" by knowledgeable people).
WEP128___(A little Harder, but "Hackable" too).
The three above are Not considered safe.
Safe Starts here at WPA.
WPA-PSK__(Very Hard to Break).
WPA-AES__(Not functionally Breakable)
WPA2____ (Not functionally Breakable).
Note 1: WPA-AES the the current entry level rendition of WPA2.
The documentation of your Wireless devices (Wireless Router, and Wireless Computer's Card) should state the type of security that is available with your Wireless hardware.
All devices MUST be set to the same security level using the same pass phrase.
Therefore the security must be set according what ever is the best possible of one of the Wireless devices.
I.e. even if most of your system might be capable to be configured to the max. with WPA2, but one device is only capable to be configured to max . of WEP, to whole system must be configured to WEP.
If you need more good security and one device (like a Wireless card that can do WEP only) is holding better security for the whole Network, replace the device with a better one.
Setting Wireless Security - Configuring Wireless Security
The Core differences between WEP, WPA, and WPA2 - Wireless Encryption - WEP, WPA, and WPA2.