OS - All Windows platform
Build :- 79 (Can reproduce with older builds also )
Hardware - Intel

Steps to Reproduce :-

1. Double Click Windows based JDK installer to install JDK
2. Accepting License and select destination folder for JDK
3. See "Select Component " Dialog box
4. Uncheck and Check various components , Program Files , native Interface Header files , Demo Files etc. to verify "Space required on drive" gets updated accordingly
5. Uncheck and Check Java 2 Runtime Environment Option , Space required remain unaffected
6. See attached images for clarification

In brief :-
"Space required on Drive" does not get updated on Selecting and deselecting Java Runtime Environment Option while installing JDK1.4.0-beta3 for Windows