Probably a good idea, but keep in mind that (a) if it's business data, they won't know what it is unless you've somehow identified it; (b) if it's porn, chances are they've seen a lot worse and have had plenty of time to copy it; and (c) in any case, the risk of losing files to someone stealing your laptop is way greater than the risk of someone in a repair shop using them for mischief. Repair techs know any use of stolen data could be traced back to the shop and then directly to them. That would be a career-ending move. Unless it would be worth a heck of a lot of money with nearly zero risk, it ain't worth it.

In other words, don't have anything on your laptop that would cause a major problem if someone stole it. If you follow that guideline, you'll be fine with the repair shop too.

If you're still concerned, anything that erases data files (not just directory entries) will do fine. You don't need the kind of program that goes over the surface sixteen times with alternating 1s and 0s or whatever. They're not going to use the kind of tools that detect the stray bits of magnetism left over after normal data erasure.

There was a DOS share/freeware prog called Wipe (I think) that I used for deleting the contents of floppy discs before passing them onto other people at Uni (long before the days of flash drives). All you did was load it onto the disc, type wipe*.* and it wiped everything including itself.

It used to overwrite things with 1s and 0s, or that was what it said it did, someone tried to recover something off one of my second hand discs and said they had no luck using Undelete and I think something commercial they had access to through the Uni. They were after a picture that I had taken and scanned of them and were very pleased when I said they could just have the original. No idea if it is still floating around on the net though.

I've seen someone on tv burning their hard drive to kill the data "once and for all".

And whilst on the subject though a little OT the US Government used to shred documents into small cross cut strips, which the Iranians had sorted and stuck back together from the Tehran embassy documents. They now I've heard have something that grinds paper into a fine powder (which is then destroyed or recycled) to ensure unreconstructability (is that a word?) of the original, as there are computer progs that can reconstruct images of stuff that's been through a simple shredder.

Another vote for eraser
 

There is also a portable version that will run from a usb drive. Eraser Portable

used eraser for years works great!

I like BCWipe (and that might be what Jimmie76 is recalling. (http://www.jetico.com/download.htm). They pulled their DOS version, but their Windows version is quite smooth. Delete with Wiping. Wipe free disk space. Wipe special folders. Wipe Recently Used Lists. Swap File Encrypting utility. 39-day trial. (No, I don't work there or own stock, or get a commission; I just like the thing!)

Since you were wondering, I'm a lawyer. There are all sorts of things we keep on computers for which we have an obligation to keep confidential.

Thank you all for your suggestions!