Right, I've got version 1.6.0_32 and 1.7.0_05 installed on my Win-7 64bit.
If I keep 1.6 the only one activated, it works with the browser, 1.7 doesn't. Neither appears to be installed nor works for db_manager, according to cmd.
cmd says:
"Java" isn't recognized as internal or external command, executable program or file batch.