Invisable Worm?

I have been trying to work out exactly what is wrong with my computer for a long while now. Every so often, my computer tells me that my windows partition has low space... I have multiple virus and malware checkers, and none of them can find it. I have also been through hijackthis and seen nothing I think is amiss... Here it is anyway, just incase I'm missing something:


Edit: Removed inline Hijackthis log


I also cannot find any files which have replicated themselves, bar the annoying MSN Live files...

I really don't want to have to wipe my harddrive again, I've lost a lot of information to that ruddy WinAntivirus, and I don't want to be defeated again!

U can email me at halfbakedtriga
the usual hot male com variety.

Thanks if anyone can help...

P.S. other simptoms inlcude:
My start page was hijacked, and set to livesearch, and I was locked out. I've managed to change it via regedit, but I'm still locked out if I go via internet options, and was until I changed the option, locked out via tools-> internet options. It also started when I downloaded an installer (via a pop-up window, like the regular windows update pop-ups when u have it set to auto update), and when it installed, all the above started to happen -although not sure about the worm like aspects - along with the title bar of every internet explorer saying "windows live search... blah blah ...the internet, a place for porn, viruses and malware, play safe!!" which I thought was especially ironic, as it's blatently some form of malware that's done this...

:major