What tools are you using?
For the marquee, paint bucket, pencil, and lasso tool you should uncheck the "Anti-Alias" box at the top. For the eraser make sure it is set to Block mode.
Keep using photoshop, with its layers you will discover that it is hands down the best tool for the job.
Edit: Do not use the line tool. Rather use the Pencil tool (available as the alternative to Brush, right click it on the toolstrip and select Pencil) at 1px diameter. Click the start point of the line and then shift-click the end point to create neat MSPaint-style 1px lines in Photoshop.