"Straightening-out" Vista ...

I really don't know where to begin.

I have some Firefox "issues", however, as they may take me some time to get a grasp on (get worked-out), I'd like to ask a couple of Microsoft (Vista) OS questions ...

1. In Vista (Home), I am currently using Defender exclusively for Start-up control (I suppose that is "best" - for now?).

Previously, in XP, I had been instructed that I could (should) block Java (in "StartupCPL") from starting at startup, in the name of "speed/performance" (trying to squeeze-out any that I can).

In Defender, I see two entries for Sun/Java, one is: "Current User", the scheduler/Auto Update, I suppose - jusched.exe = "Disabled".

The other is Local Machine, the Platform (JRE?) SE 6U13 (which I suppose is the program in its entirety?), and which is also "Disabled".

May BOTH of these be disabled without trouble? If I leave them that way, I will have to check (manually) for updates on, what, about a monthly basis - if they are left disabled like this?

Secondly (and lastly for this eve.) in the process of getting a Malware Check-up (from the "neck, up", mostly) I discovered in my (rather incessant) poking-around, that the Recycle Bins in 4/5 user accounts was set to a seemingly ASTRONOMICAL amount of space usage/reservation ("13454MB" in C:\, and "1023MB" in the D (backup) drive (!!).

What is a typical/average/normal amount or % to have these set for? I have (technically I suppose) 222GB in C, and 9.99 in D. - total space.

Thanks in advance - & I appreciate/welcome ALL replies.