Can you use the oyster card in the towns of Slough and Windsor? Thanks
No, the Oyster card is only valid within the London fare zones, and both Windsor and Slough are separate towns.
There is an interesting exception in Slough as the 81 bus to Hounslow is a TfL service.
If this is to get to and from Windsor to central London you can pay for the trains with a contactless card but not Oyster.