OK, this may be a silly question but...

I have inherited a project and am tasked with going over the primary key relationships.

The project largely uses Guids. I say "largely" because there are examples where tables use integral types to reflect enumerations. For example, dbo.MessageFolder has MessageFolderId of type int to reflect

public emum MessageFolderTypes
{
inbox = 1,
sent = 2, 
trash = 3, 
etc...
}

This happens a lot. There are tables with primary keys of type int which is unavoidable because of their reliance on enumerations and tables with primary keys of type Guid which reflect the primary key choice on the part of the previous programmer.

Should I care that the PK schema is spotty like this? It doesn't feel right but does it really matter? If this could create a problem, how do I get around it (I really can't move all PKs to type int without serious legwork and I have never heard of enumerations that have guid values)?

Thanks.