My Linksys WRT54g router WPA-PSK field takes 64 characters. My Sony Z1
(with built in Intel-Pro wireless 2200bg and running XP-Pro) network
key field will only take 23 characters. Why the difference?


Computer has all the lastest windows updates. Wireless card and router
have the lastest firmware updates.

Thank you for your question.  
 
However, I believe that to answer it well, your question will require
more time and effort than the average amount of time and effort
associated with this price. Here is a link to guidelines about pricing
your question, in the pricing guide:
https://answers.google.com/answers/pricing.html

WEP means Wireless Eqivalency Protocol
WPA-PSK means Wi-Fi Protected Access - Pre-Shared Key

WEP keys are either 40 bits long (referred to as 40 bit
encryption) or 104 Bits long (referred to as 128 bit encryption {they
count the 24 bit IV).  Since the valid hex characters are 0-9,a-f,
they represent 4 bits.  A 40 bit WEP key is 10 hex characters long and
a "128 bit" key requires only 104 bits and is 26 hex characters long.

The WRT-54G can take a WPA pre-shared key of 8-32 Characters in the
Pre-Shared Key according to the product literature.  The newer code
may support an AES version that has a larger 256 bit key capability.

http://www.linksys.com/products/product.asp?prid=601&scid=35

However, if a 256 bit key can be specified, the WRT-54G can take a 64
Hex character key.

Without seeing which model of Sony Vaio Z1 you have, it's likely that
it uses a shorter WPA Pre-Shared Key thank the Linksys WRT-54G
wireless router.