Where did you create the vanity address? Did you have 2-factor set up? You don't need to throw out your comp but I wouldn't use it to store or send bitcoins unless you know its safe as you could have some keylogger malware.
Im throwing it away :-( i already have new one paid for i was about to go pick up before i seen this
reload the os on it and use it as an offline pc to sign offline transactions for your cold storage wallet.
add keypass vault........... http://keepass.info/ ... to your offline pc as well too store all your online passwords (this well help you use more than one different passwords per website and stronger pws too) .
you can keep your keypass file on a flash drive as well so you can access it from any pc you install keepass on ..
back all this up onto another one or two flash drives you put into hard storage (you will have to update the keypass files every now and then as u add more pw's to it) .
if you use the same password on different websites you could be compromised this way too .