In the past couple months I've had to rapidly replace several laptops, and I had to learn the hard way about a "feature" MS introduced with Win7. I have work files that I can't access at the moment because of this "feature".
You really should be using online services or some content server for critical files, and I can explain why.
Whenever I switch to a new computer, I generally pull the hard disk from the old one and then put it in an external USB enclosure to copy the important files off of it. This doesn't work anymore with Win7.
First, Win7 won't let you grab all the files and folder on a partition and simply copy it elsewhere. I used to do that with WinXP, but with Win7 a lot of files are lost in the process. If you want to copy a large volume of files you'll need to use a partition tool to copy a partition.
Second, if a partition on your hard disk was originally made with Win7, you won't be able to access it after you pull it from the original computer. You will be blocked. I have files sitting in what used to be the desktop folder and I can no longer get to them.
If I had been smart I would have used Dropbox, Flickr, and other online services to store a copy of those files. In particular, I like Dropbox for this, and that's mainly because you can point it at a folder and tell it to sync that folder with the online storage.
I didn't lose more than about 100MB of data, and I know I can rebuild it. But it is exceptionally frustrating because MS has changed the way their file system works. I've used DOS and Windows for going on 20 years now and I'm used to doing things a certain way. Now it's changed.
image by phil_g