Hi,
please refine, what you mean by "I cant upload". One known issue in the past was, that with certain constellations of Firefox, Windows XP and Alfresco, the ajax components in the documentlibraries where not displayed (the contents, the buttons "upload" & "create folder".
Several people had this problem, but the solution for this is unknown to me, just that it has disappeared by now. maybe due to a plugin-update on my side, maybe something else. You can check out the online trial community. I could reproduce this behaviour there as well, meaning it is a client problem, not one on alfresco-installation side.
Norgan