Photoshop CS shows different colour image comapred to when saved as JPEG

Hi ,
I recently started having trouble
currently im using adobe CS

and no matter if i work in CMYK or RGB when i save the file as a jpeg ready for the photolabs, the tone/colours of the picture are different to what i see in photoshop. (but if i open the jpeg file through windows and not photoshop , the tone of that picture is how it prints.) I dont know why photoshop is showing me something differents,
If you could plz help me i would be soo thankfull
plz email me

Thanks heaps

Jow long since you last calibarated your monitor? They do drift. Once a month is recommended. Re run Adobe Gamma - or your third-party calibration solution - that should sort it out for you.