To upload a picture from "My pictures" on XP just click on "Additional Options" under the text box when you are posting a new topic and then click browse in the upper box for your first picture and this will take you to you stored photo's on your PC. When you find the one you want to post then select it and wait for it to appear as a heading title in the browse box. If you want to selct a second photo then go to the lower browse box and repeat the process. Then post!!!
Hope this helps