You could have SQL Server assign the values when records are added. You can use a uniqueidentifier column and mark it as the RowGuid, which will get a default using the NEWID function).
If you need to create the guid from Infopath, you can create a new guid using C# or VB with System.Guid.NewGuid()
Jim Cantwell
InfoPathDev - Redmond
Jim Cantwell
InfoPathDev - Redmond