boy do I feel old...
1. get into the directory that has the files you want to delete. If your files are in C:\Runs\Old for example, and you are starting off in C:\, then type "cd Runs" (without the quotes, I just put those there to show you exactly what to type. And cd = change directory) and hit enter, then "cd Old" and hit enter to get there. "cd .." will move you back up a step.
2. figure out what files you want to delete. If you want to delete oldrun1.gct, then type in "del oldrun1.gct" and hit enter (del = delete). There is no trash can in DOS, once you hit the enter key it is gone forever.
3. if you want to delete a bunch of files at once, use a wildcard: "*"
If you type in "del *.gct" it will delete every single file in that directory that ends with .gct in one fell swoop. Be careful with this, you can accidentally delete a bunch of stuff you were intending to keep.
John