Use Firefox as your browser not Internet Explorer. Windows XP had IE6 and will update to IE8 but that is still an out of date browser which could be the reason for the error message. Firefox works on WXP. I would recommend updating to Service Pack 3 if you can find it to download.
What is Markdown?
Markdown lets you add more formatting to your post. Simply type in your post and it will display as written.
If you wish to add bold or italic characters, add a hyperlink to another website, a heading or a horizontal line, simply use the relevent icons above the text input field.
A preview of your post will appear in the grey box below. If you make a change and you're not happy, simply press the back arrow icon to undo.