I don't know if you still need it, but this guy has on Ebay a restore DVD for this Stylistic model. I had same issue with Stylistic P600 and it fixed it in a snap, a since then everything just runs smoothly. Cool thing is that its been only 9 bucks and he ships worldwide.
Here is the link for one of his auctions Restore DVD Fujitsu Stylistic C-500 e P-600 su eBay.it Fujitsu Siemens, Computer portatili, Informatica e Palmari .When i first found one, it was expired but lookin for other auctions from same seller did the trick ;-)