A heavily fragmented drive can have a similar effect( as in making programs unresponsive), a pile of viruses sounds bad nomater how you stack it; you can debug the drive off another system for the most part, you can also reload some antivirus software and have it scan first, make sure her connection to the internet is disabled, shouldnt have to reformat; the generall guides for safe removal suggest safe mode becuase safe mode starts up only what is needed to run your system, viruses often run without any indication in the background.