I just need some tips on running a server on 4 gigs of ram...

I run a private server of mine with 4 gigs of ram on a dell laptop(I know 4 gigs and a laptop isnt a good idea for running a server). My operating system is Windows vista home premium. (copyright 2007). I have a 32 bit operating system. . I use bukkit for my server. I have LOTS of errors. I get the "Cant keep up! Did the system time change, or is the server overloaded?" I get that ALL the time. Here's another error:

[SEVERE] at java.net.SocketOutputStream.write(Unknown Source)
2012-01-23 11:18:11 [SEVERE] at java.io.BufferedOutputStream.flushBuffer(Unknown Source)
2012-01-23 11:18:11 [SEVERE] at java.io.BufferedOutputStream.flush(Unknown Source)
2012-01-23 11:18:11 [SEVERE] at java.io.DataOutputStream.flush(Unknown Source)
2012-01-23 11:18:11 [SEVERE] at net.minecraft.server.NetworkWriterThread.run

These are the plugins i use:
-Chunk Load
-My World
-Essentials
-World Edit
-World Guard
-LWC
-Jail
-Mobrain
-Chest shop
-Iconomy
-explotion revert 2.1
-Stop Cursing

Here's a question i have: Whats the estimated amount of People i can have on my server at once?
Thanks for your help!
-Andrich2000

I almost forgot! The version of craftbukkit i use is CraftBukkit -1.1-R1-SNAPSHOT.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Ok so , Windows Vista takes up 34 % of your computers ram , Minacraft takes 43 % and all your other programs maby 20 % . So what is left to your server ? well not enught , I recommend you to don't Use vista , ( It takes up all your computers Ram and Cpu ) And maby play minecraft on another computer , Note: you have alot of plugins , They take more ram , So try to delete som plugins you dont need

 

Vista will just eat your computer data. I think windows xp is better than vista

 

If you really want to run this server I would recommend using Ubuntu, it only uses 4Mb of ram compared to Vista's 1Gb so it will run significantly better

 

I think 4MB is a little low, even my CentOS uses like 100MB of RAM steadily.