Java Error opening registry key

Make sure you remove any java.exe, javaw.exe and javaws.exe from your Windows\System32 folder and if you have an x64 system (Win 7 64 bits) also do the same under Windows\SysWOW64.

If you can't find them at these locations, try deleting them from C:\ProgramData\Oracle\Java\javapath.

You will find a folder named "Oracle" on ProgramData folder in your windows installed drive. Remove the folder. Hope it will work.In my case my install drive is C and my path is C:\ProgramData\Oracle

I had a similar problem. I had installed JDK7 update 1 but couldn't use it (probably because I found a JRE6 that I deleted after installing JDK7). Uninstalling JDK7 was impossible. The solution was to add the JRE registry entries by hand.

[HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment]"CurrentVersion"="1.7"[HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\1.7]"JavaHome"="C:\\Program Files\\Java\\jre7""RuntimeLib"="C:\\Program Files\\Java\\jre7\\bin\\client\\jvm.dll"[HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\1.7.0_01]"JavaHome"="C:\\Program Files\\Java\\jre7""RuntimeLib"="C:\\Program Files\\Java\\jre7\\bin\\client\\jvm.dll"

You'll have to adjust the above to your own directories and version.

If this doesn't help, there's still JavaRa https://singularlabs.com/software/javara/ .