Vista - WLM2009 web cam

a question pls ..
i have downloaded the new wlm2009 my notbook computer and its quite old its
a compaq presario 2700 that has an

adapter type>> mobility radeon
chip type>>> mobility radeon AGP (0x4c59)
DAC>>> internal DAC(350MHZ)
memory size 32MB

now the issue is when i open the web cam on it i have two choice for the
size of the cam that it could let me select from Small and Medium only and
there isnt the large size option.

so i tried uninstalling the wlm2009 and re installing the wlm version 2008
and tried the web cam i was able to have the three sizes choice small medium
and large.

any ideas as to why please, or what could be done to solve this issue??
thank u