possibly the reason that registryprot told you about this systemtray thing is that it's actually finding some malware wanting to reinfect you and it happens to be masquerading as what you think is a valid process.. ie systray.. and i think you said.. "ok go ahead, reinfect me"
post your hijackthis log.. you must of missed getting rid of something.
mediaplayer.. I know about this one..
I've seen a number of hijackthis logs with this entry..
F1 - win.ini: run=C:\WINDOWS\System32\services\wmplayer.exe
google it.. you'll see that this is known as the W32.HLLW.Gaobot.EF trojan
http://securityresponse.symantec.com...gaobot.ef.html
it also wouldn't hurt to get a few trojan scanners in addition to any av scanners you might have.
