Please help: IE8 browser extensions unrecognizable

My IE8 browser has 4 extensions which are unrecognizable and could not be disabled.Could someone tell me what they are? Is my browser hijacked?

{219C3416-8CB2-491A-A3C7-D9FCDDC9D600}

{789FE86F-6FC4-46A1-9849-EDE0DB0C95CA}

{2670000A-7350-4F3C-8081-5663EE0C6C49}

{DFB852A3-47F8-48C4-A200-58CAB36FD2A2}

The OS is a 32-bit Win7 Ultimate.

Thanks a lot for your help.