I can't count how many times this utility has got my customer PC's up and running - it cleans out malware that others can't.
PDFcreator - for converting any printable image into a PDF file
Freedownload manager - great for managing downloads (I use it to download podcasts into a specific folder which is then sync'd with my phone)
PicPic very handy image editor
+1 Sysinternals Suite