Java builds:
WIN95 www.oldapps.com/java.php?old_java=7
WIN98/ME www.oldapps.com/java.php?old_java=52
WIN2K http://www.oldapps.com/java.php?old_java=6281
Java.com also has a downloads archive but requires an account (free?), but it's bloody well hidden.
Depends on the hardware tested, but yes, running Spi32/W1024 on Pentium 1 will set you for 30 hours+. Do remember Wprime has an issue when a run takes over 24hrs, make sure you revert the OS time back every 23ish hours.
Yes, you can't validate frequencies with CPU-Z on stuff older than XP, but for screenshots only you could use any version. Socket A was particularly buggy with CPU-Z on *some* boards, feel free to browse this forum for solutions, I believe there's even special builds of cpu-z for some older sockets.