I doubt it, a burn folder is just a temporary folder that hold aliases of the locations of files so you don't have to move the orignais.
One you burned a disk and are done, you simply trash the burn folder.
However Hotmail is a dangerous place, you REALLY should opt to use GMail. Yahoo mail is kind of safe, they had malware on the adds on their site though.
Apply your Software Update, download the free ClamXav and run a scan on your drive just to see if you have downloaded something.
Also you should consider upgrading to 10.6 as this allows you to keep using more recent versions of Flash which are more secure than 10.5 versions. Also 10.6 strips out a lot of PowerPC code your not using, makes your computer faster with video driver updates.
Also run ALL of the free OnyX's cleaning and maintainence aspects for your OS version and reboot, should clean out the caches and possible glitches this might be.
http://www.titanium.free.fr/