I sometimes have problems with cookies on the linksys site so

http://www.linksys.com

Go to support
(choose North America and US as appropriate)

Choose Linksys Windows Vista Support on left blue bar.

Choose Download Drivers toward center of page

the 5th line under adapters is USB200M V2 (version 2 of the adapter) - if this is your adapter's version (there is a version 1 of this adapter too) there appears to be a 32 bit Vista driver.