Another option is use a picture sharing site like pix.ie or flickr.com
You then only need to e-mail a hyperlink.
pix.ie allows the viewer to choose different sizes to download/view (depending on what was uploaded)
If you select all the files you want to send and right-click on them and select 'Send To'->'Mail Recipient' XP should prompt you to reduce the size of all the images selected - does it not do this?
Imagemagick provides a powerful command line interface that can be scripted to manipulate multiple images.
if you have microsoft office then go into your program list and then microsoft office, microsoft office tools and microsoft office picture manager should be in there. Allows you to compress picture by going to picture - compress picture
Irfanview does indeed have a Batch Conversion that allows multiple files to be converted and resized if necessary. Great piece of software. The Batch menu can be found under the File menu path.
I use JpegSizer - you can select a whole folder at a time.
There's a free 15 day trial and its also very cheap to purchase.
Has options for every size of photo you could possible require.
If you are using Outlook to send the images you get an option to reduce the size of the images you are sending (a screen prompt comes up asking to resize or send original size) - very handy if the only reason you need to resize is to send by email.