I have a MikTeX/WinEdt installation and I'd been using the "PDFTeXify" button to create PDF's that automatically open in Adobe Reader.
Somewhere along the line I opened GSView and accidentally told it to associate PDF's with GSView, and now whenever I "PDFTeXify" it tries to open the PDF in GSView but fails for some reason. I uninstalled and reinstalled both GSView and WinEdt, and made sure that Windows recognizes PDFs to be opened with Adobe Reader (right click a PDF file in Windows Explorer -> properties -> Open with...). When I reinstalled GSView I made sure to tell it NOT to associate PDF's with GSView. However, somehow the change seems to have stuck and PDFTexify still insists on opening in GSView and not Adobe Reader.
Any ideas on how to fix this? I'm assuming/hoping there's an option somewhere that sets the default program/reader to open PDF's when you compile but for the life of me I can't find it.