in .NET 1.1, I wish to do some xml searching/node searching using xpath and an xml string.

I have this xml here:

<caller><userid>{540C8042-A520-DC11-AE79-00132047A063}</userid><merchantid>{59344736-A520-DC11-AE79-00132047A063}</merchantid></caller>


how can I obtain the <userid> value (the GUID) from that given string?