How can I switch different JRE in one PC

Question

I am sorry to post it in this forum because I post almost the same in JRE forum but I don't get any help there for 2 days.
My problem is that I have two systems to be used in different JRE enviroment.A system can only run in JRE 1.3 and B system can only run in JRE 1.5 enviroment.But I have to run both in one desktop(which use WinXP SP2),how can I do it . I tried some methods like below:
Method 1:
I Edited the registry using the cmd of regedit , edited some like these.But it did not work .
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{08B0E5C0-4FCB-11CF-AAA5-00401C608501}\TreatAs]
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{8AD9C840-044E-11D1-B3E9-00805F499D93}]
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{8AD9C840-044E-11D1-B3E9-00805F499D93}\InprocServer32]
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\JavaPlugin\CLSID]
[HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Development Kit]CurrentVersion="1.X"
[HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment] CurrentVersion="1.X"
Method 2:This method is post in http://java.sun.com/j2se/1.5.0/docs/guide/deployment/deployment-guide/jcp.html#java as belows:
Example:
Assume you are running on Microsoft Windows with Microsoft Internet Explorer, have first installed version 1.4.2, then version 5.0, and you want to run 1.4.2.
Go to the j2re1.4.2\bin directory where JRE 1.4.2 was installed. On a Windows default installation, this would be here: C:\Program Files\Java\j2re1.4.2\bin
Double-click the jpicpl32.exe file located there. It will launch the control panel for 1.4.2.
Select the Browser tab. Microsoft Internet Explorer might still appear to be set (checked). However, when 5.0 was installed, the registration of the 1.4.2 JRE with Internet Explorer was overwritten by the 5.0 JRE.
If Microsoft Internet Explorer is shown as checked, uncheck it and click Apply. You will see a confirmation dialog stating that browser settings have changed.
Check Microsoft Internet Explorer and click Apply. You should see a confirmation dialog.
Restart the browser. It should now use the 1.4.2 JRE for conventional APPLET tags.
I tried this method but it did not work either.
By the way , the method I use to check whether the switch of JRE versions is work correctly is this :
1.Create a html file which contains OBJECT tag
2.Double click the html file and then check the information in the java console in the window's taskbar.
3.What the java console says is the JRE version I am using now
Is this check method right?
I found that many people confronted the same problem like me but they resolved it by the method of changing control panel, so I am doubt about the check method.
Can anybody give me some help?
Thanks a lot in advantage.

Answer 1

Some additional information:
I tried the method of changing control panel by JRE1.3's control panel to change current JRE enviroment to JRE1.3 (see http://java.sun.com/j2se/1.5.0/docs/guide/deployment/deployment-guide/jcp.html#java), and I found that in the IE->Tool->Intenet Option->Detail Setting Panel the JRE version used in IE had been changed to JRE1.3 really.But when I connect System A(which use JRE1.3) use IE,the started java console is still JRE1.5 and some applets can't run in the enviroment.