Is there anyway to do this? I know I can require approval, but was thinking more along the lines of stopping new accounts from being made. Perhaps by removing the link completely?

Wanted to put the site on a lockdown mode of sorts - I see I can mass disable everyone's accounts, but that's only half of what is needed.

There is not currently an option to do this.

You could use the Advanced Layout Options and jquery to accomplish this.

If you add this to the very end of your layout file, you this should disable the "Create An Account" link:

<script type="text/javascript">
jq("a[href$=editprofile.php]").hide();
</script>

But that will only disable the link. It won't disable it if someone types in the editprofile.php link directly.

I put it at the end of the layout file, but it doesn't seem to work.

Confirmed the code is there using view source option in IE8/Firefox.

You're right. I'll have to look into this more.