Editing the config.lcl file shouldn't hurt. That may not work and it could cause a problem, but it is easy enough to reverse the changes in that case.
Try running the configuration program, hit the reset button, change the resolution and save (you can skip the test). This should re-create the config.div file. If not, the default versions of config.div, slashed.cfg and slashed-d3d6.cfg can be downloaded
here (1KB).
The configuration program file should be named configtool.exe (and is 184KB). The config.div file should be shown as 1KB (if so, try opening it in a text editor). If your config.div file is shown as 184KB (or basically anything higher than 1KB), then I would try running a ScanDisk (right click on the hard drive in Windows Explorer, select Properties, switch to the Tools tab, and hit the Check Now button in the Error Checking Status section). If no errors are found, you could backup your saves (just in case) and re-install the game.
