It isn't possible. Check HTML code is available for HTML like languages - it means HTML multihighlighter, HTML and XHTML highlighters. It has no sense to use HTML check for TXT e.t.c.
Are you sure you are running PSPad from folder where is PSPad.exe + Tidy.exe in same folder? Developer builds contains missing files only - read the info in build page. -- <http://forum.pspad.com/read.php?6,65618,65632> PSPad freeware editor http://www.pspad.com
