IPSec on Win2k/WinXP: per-user-certificates possible?

Hi, i have a little problem with understanding how windows manages certificates. i have running a freeswan-server (suse 8.2) and multiple Win2k/WinXP- roadwarriors. in windows the certificates are located in "local computer". so every user at this machine can establish an ipsec-connection with this certificate. my questions: - how can install the certificates per-user? - if more than one certificate is installed on one machine, how can i ensure that only a specific cert is used for every user? thx, andy