I'd see it as just another tool in the anti-malware armoury. You can update the definitions (presumably 'in memory' if you have booted from a CD or DVD), but probably the best medium to use is an USB Flash Drive, where (I presume) the updated definitions can be written when downloaded from 'the internet'. The Full scan on my 20-odd GB C: drive would have taken about 5 hours, I reckon, so I cancelled it after half an hour and tried the Quick scan, which took about 5 minutes. Those familiar with Windows Defender and/or Microsoft Security Essentials will note a remarkable similarity in the interface, although all the dates and times are in US format (boo.). I tried the 32-bit version of Microsoft System Sweeper beta on XP Pro, and it required me to install IMAPI v2.0 (and reboot) so that it could burn the CD from the 205.5 MB download.