RIS leaving two Operating Systems after install

[Pakled]

Lately we've been RIS'ing some Dell Latitude E6500's and Optiplex 760's. While everything seems to load fine at first I have noticed something unusual after the "39 min" install portion. When the system reboots it comes to a screen asking me to pick which operating system I want to boot to. Both are Windows Xp but there is only one partition on the drive. I have also noticed that if I Re-RIS the same machine that it does not do this the second time thru. Has anyone else experinced this.