nganvu--Did you try the test to see if you have any Java (or Virtual Machine) on your PC? It sounds like you have Sun's Java. You will not get update messages from MS about Virtual Machine. And Sun will not send update messages unless you have Sun Java already installed.
If you are getting an update message, can you just follow instructions and update? Or else go to the site mentioned by Steve R Jones. If you are going to have Java on your PC, you might as well have the latest version.
Yes, the two versions of Java usually get along. You can check IE Tools|Internet Options|Advanced tab|Java to see if you possibly have only one checked as the default version to be used, anyway.
On another subject
I have a PC with Win XP home edition. After updating to XP SP2 it became WinPro
That is not possible, unless you updated to SP2 by using an update (or full) version of WinXP Pro SP2. Updating WinXP Home to SP2 from MS Windows Update or download sites will only give you Windows XP Home SP2.