I believe this will be because when you open a folder it examines the file and tries to put a little thumbnail on the left etc. If I'm right then in your case it doesn't recognise the type and gets confused.
If you know how to copy from DOS you can probably get them off the PC that way, but I imagine finding them would be a big job.
If you search for them without going into the folder does that crash it too? Suppose in the folder above (or by right-clicking the drive in My Computer) you do search. If you know the type you can search for *.avi or whatever.
If it lists them that way it may not crash and may let you select them to copy to say a flash drive.
Another idea may be to post the type of files. If they are unusual you may need to install a codec so windows can recognise them and not crash any more. If they are standard picture types then something is broken in windows and needs fixing.
If this is a recent problem it's possible something in the operating system is corrupted and that system restore might fix it. I hate system restore, but if you've not changed anything important or installed new things then it's relatively safe to use. The trouble is that the problem may have started weeks ago without you knowing and restore is only good for a day or two.
I've also seen this fix in a few places which stops windows trying to preview media files which ought to work.
In the run box on the start menu type in
regsvr32 /u shmedia.dll
If it doesn't help then you can type this in to put it back.
I just tested it on mine and it seems safe enough. it just makes windows stop trying to show a preview of the files in the folder.