When you open up the folder that they are in, if you know which pictures you want, you can select any consecutive series of pictures by selecting one, and then holding down the Shift key, and then clicking on the last one. Then, press delete. If you have pics located throughout the folder (interspersed among some that you want to save), you can press down the Control key and then click on the ones you want to delete. When you are done, hit Delete and then OK.

Does this do it for you?