Why are photos viewed in Windows darker than when exported from Aperture?

Ok, so I'm taking some photos for work on a Canon 40D. The profile in the camera is set to sRGB and the RAW photos are being imported into iPhoto.

Some of them are then being imported into Aperture for processing and then exported from there as Jpegs into a folder. As far as I can see the profile again is sRGB.

When I get them to work, running windows xp / photoeditor etc, they all appear dark almost underexposed, and if i open in Photoshop it also says the workspace is using sRGB but the colour profile of the photos is Generic HDR. How is this so?

Is the imac adding the generic HDR profile to the photo or is it being added at the iPhoto stage? Should I just import to the computer via image capture and then import into Aperture? Why is this happening?