Tekkit Classic Server problem?

[astoria]

I got the Tekkit Classic server and had it running and everything. But it wouldn't let me OP myself. Even in the OP file. I put myself on the OP list but still nothing. So I deleted the entire file so I could try to redo it. But it deleted only half the files and the rest won't delete because they're open in Java. It lagging my computer and I don't know what to do. How can I delete the server files..?

[ElPolloPicante]

To op yourself, you will need to use the console. Just type in op <username> and it should work. If your hosting the server on your computer, it probably can't handle it, hence why it is lagging.