Doubt duprepare and dushare

Hi,
I have difficulty in understanding duprepare and dushare. First of all is
this for hotfixes only or can this be applied to service packs as well? (I
know very well that slipstreaming service packs works fine but I just want
test this one)
Well I tried from a windows 98 computer to install windows xp sp2 and I left
sp3 updates in a folder named updates then I prepared the dynamic updates via
winnt32 /duprepare:c:\updates (a screen appeared and wentoff)
afterwards I ran winnt32 /dushare:c:\updates and I thought that windows 98
would be upgraded to windows xp sp3 but I got windows xp sp2. Will you please
expalin what was wrong? Thanks in advance.

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Regards
Regunathan Umapathy BSc, A+, MCP, MCDST

Umapathy (உமாபதி)