JRE Autodownload is not proper on windows multiboot systems

JRE autodownload is not working as expected on windows machines having more than one OS installed.

In my PC, I have installed Vista in C drive and Windows XP in E drive.
When I am using windows XP,
if I download any JRE bundle and install it (manually) ,the JRE Installation directory is E:/Program Files/java as expected.
But when I launch an application that requests autodownload of another JRE ,the JRE installation happens under C:/Program Files/Java.

I used these files that require JRE 1.4.2 and 1.5.0 .
http://web-east.east/www/tests/1.6.0/6298822/test4.jnlp
http://web-east.east/www/tests/1.6.0/6298822/test5.jnlp

In another windows machine chinnu.sfbay.sun.com (AMD64 WinXP) there are 3 OS.

C: Win XP 32
D: Vista 64 Enterprise
G: win XP 64.

When the system is booted in Win XP 64 and the same jnlp files are launched, the JRE gets installed under C:/Program Files/Java