There is a couple of ways you could do it. If you company allows you to download a free program, this program will allow you to easily resize pictures.
Download IrfanView Another way, it to go to a photo hosting site, like photo bucket, and upload the picture there, it has a feature that allows you to resize pictures. If you can upload it to this thread, I could resize it for you, also. Just go to the bottom of the page where it says manage attachments and try uploading it to this thread, if it really large it may be also too big for this thread too, but I think it will take an 8 by 10 picture.