Computer Hacked(30GB)...ideas on where/how to search for files stored?

Boyfriend's computer was hacked and about 30-35 GB has been used up - I'm in IT but am a DBA, so this is not my area of expertise. I'm trying to figure out where these files could be hidden so we can remove them. Any ideas on a quick method? Am assuming they are videos/pictures/music because of the extreme size, but nothing shows up when you use file search. Operating system is Windows XP. Also, he has firewall, virus protection, and spyware protection - what else does he need to avoid future incidents?

Computer Hacked(30GB)...ideas on where/how to search for files stored?ktm

Here is a program that will show you what folders are using the most storage space.

http://www.topshareware.com/DirSpace-dow...

The program shows freeware. Like everyone else mentioned, download AVG and ZoneAlarm (both are free) and use them to prevent something like this from happening again.

Computer Hacked(30GB)...ideas on where/how to search for files stored?nortan

I don't mena to be presumptuous, but certain sites are a definite red-flag when it comes to being succeptable to hacking. Also, it can depend on the instant messenger he is using. Try this link and download the trial version:

http://www.download.com/Security-Task-Ma...

I can't guarantee it will work, but this shows you all of the systems that are running and allows you to shut them down and/or quarantine them. Sometimes if an application is running in the background and you have no way of knowing it, it can allow a hacker access to virtually anything. I hope this helps!
Use the search feature of Windows Explorer. In the advanced section you can specify a size range. Look for some big files. FWIIW hope it helps.