Use the command net localgroup Administrators to produce a list of all members of the Administrators group, then check if your user ID is in the list.
In this example, the user in question is OPR\K2M6.
C:\Users\k2m6>net localgroup Administrators Alias name Administrators Comment Administrators of this workstation Members ------------------------------------------------------------------------------- G056 OPR\CDE_LTSAltClient_DLG OPR\Domain Admins OPR\K2M6 OPR\OPR_WKSAdmins_DLG OPR\SMS2_INST_WKS_G OPR\SVC_SMS2_CLTCFG_DLG The command completed successfully.