Yes you can do this. Here is a new free and easy to use software that will
let you do this.
You can go to this site to download this new tool:
http://www.microsoft.com/windowsxp/using/digitalphotography/prophoto/photoinfo.mspx
Here is what it does:
"Microsoft Photo Info is a new software add-in for Microsoft Windows that
allows photographers to add, change and delete common "metadata" properties
for digital photographs from inside Windows Explorer. It also provides
enhanced "hover tips" and additional sort properties for digital photographs
in Explorer (in Details view)."
After you download the PhotoInfoSetup.msi file and you install it, right
click on a photo file and click on File Info on the opening menu. You can
then add/remove/change/tag etc photos in various ways. This includes
changing the date and time picture taken.