I'm trying to enable concurrent sessions on xp x64 ... I've find resolution for xp 32bit and no resolution for x64 ... Does anybody can tell me is possible to enable concurrent sessions on xp x64 or not ?

There is a patcher here, not sure if it works on both 32bit and 64bit though
http://www.kood.org/terminal-server-patch/

There is a patch for Vista 64bit
http://www.missingremote.com/index.php?opt...&Itemid=232

Sorry to resurrect a year-old post, but I'm also interested in enabling this for XP Pro x64 (SP2). The work-arounds out there are for the 32-bit version of XP. I have yet to see one for the 64-bit flavor. Anyone?

Have you tried with latest versions of course? I dont have exp with RD in WIN but i never once had this kind of issue with open source tools such as VNC.
I find it a bit weird that it is an issue at all with RD for win. According to this link, all you need is a hex editor to possibly fix it yourself, tho i didnt see it mention x64 there, it might be worth a try?

I would however, recommend you first try with the registry edits, and see if that helps.