I'm sure you know better than me but you could, write all the values
in the boxes into a temp file automatically and fill the boxes again with those values automatically when returning to "test another system"

Just a thought

Out of interest, just had a quick play this morning from my work PC, and it remembers the values I enter if I hit the back button. Am using Internet Explorer 7, so pretty outdated now, but works better than the new browsers seeing as it remembers the data entered.