I'm such a mollusc

depends what you're looking at them in.

Open windows explorer [Start, programs, accessories usually], naviagte to where your pictures are, it'll be the 'c' or 'd' drive, or whatever your external hard drive is called. Open each folder until you find them, just by clicking on the folder picture once rather than double clicking. When you find them, hover your mouse over the pics on the hard drive and see if they are the same size as the ones in the e-mail, byte-wise, it will have a bit of info, such as name, date of modification, then the size at the end.

You can find out the size of the ones in the e-mail by right clicking and select properties.
If they're the same amount of bytes/kilobytes/megabites, no worries, it's the program you're looking at them in, with things like windows viewer, there should be a line of icons along the bottom, one of them wil be 'view original size', if it's another program, you might have a little magnifying glass to increase the size, or a drop down box at the top with a percentage in it.
SOmetimes as well, you may only be looking at thumbnails of them, depending on what prgram you're using. Try double clicking on them, or right click and 'open with' a program you know will display at full size.

If they aren't the same byte size, your program has been set to shrink the size, you need to find the program name, and then go into the settings to transfer the samne size across.
That's all I can think of for now...

Cheers Taff, will have a look this evening see if I can work it out.

Sometimes around the image, it will have a number in a box eg. 12.5%. If you click on this it should give you the option of enlarging (ie 25% 50% etc)