Is a Ci File a potential attack pt. for malware?

I've a 145 GB hard drive that as of last week had less than 1 GB of space left. I've run many antivirus, spyware removal, adware removal, and more, tools. Currently, using the trial of Raxco's Perfect Disk 8.0 I've been able to defrag up to 30%...then it hangs and can't go further. I learned it is hanging at
C:\documents and settings\all users\application data\microsoft\search\data\applications\windows\projects\system index\indexer\Ci Files\0001000

Been running Perfect Disk to undo a serious fragmentation issue. My hard drive has nearly 86 GB of fragments in this particular file.
I don't know anything about Ci....can someone tell me if that can simply be deleted without killing my computer?
I could really use some serious help from someone knowledgable. I noticed that this file was created just days ago and I came home to find my hard drive nearly full!

Can this possibly be an attack on my computer? Can I delete this file? I think that would solve all my difficulties but I'm both afraid and yet anxious to delete it!
Thanks.....confused