PSU replacement

I have a Dell Dimension 4100 and i'd like to know if I can replace the PSU with a Antec SmartPower SL300S(300 watt).

http://www.antec.com/us/productDetails.php?ProdID=25300

Can I just swap out the PSU or do I have to get one that doesn't have the power switch in the back like the stock one?

Answer's yes but if you plan to fill all your drive bays and go with dual graphics cards later on, 300W isn't going to cut it.  The switch on the back is fine; it's just the I/O current switch and its placement doesn't really matter as long as you can get to it when you need to do upgrades and such.