Hi.I am installing v1.3.9.At system Inspection part of installation i got 2 yellow warnings saying

"Register Globals = ON Click here for more info"

"PHP Output Buffering (gzip) = OFF"

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My questions are:

1-what do these warnings mean?

2-How can i fix these warnings?

3-if i change these values what will be the pozitive and negative effects on my webstore?

4-Also there was this:

"PHP O/S = Linux"

But my OS is windows xp

Should i change this too?If so how?