I have baught a new Acer one AOD150-1920 Netbook, It comes with pre installed Windows XP. Problem is internet speed. In my Wifi network when I check the download speed for my HP Laptop using site speedtest.net I get 1.18MB/sec. but at the same time for Acer One NetBook download speed is just .12 MB/sec. When I tried by connecting to net using LAN wire still it's the same.I have cleaned up the registry.Stopped all unwanted services in back ground. Still its same. I can see this difference while downloading any file from internet at the same time in both of my laptops.Please help.

The bottleneck is in the hardware provided in the Acer. Changing firmware & software configurations will never make the Acer run any faster in its delivered configuration. You can disable the provided hardware & add an external internet connection but that might be cost prohibitive.

So you mean ACER AOD150 windows XP can't even have download speed of more then 200 KBPS when another Laptop on the same network is showing speed of 1.5 MBPS.
Do anyone know the highest download speed that could be achieved by this Notepad. Besides this issue booting time & response time is just perfect, there are no issues with this Notebook.

Are there any other programs or services that are accessing the internet?

Sometimes you will get some spyware, or even good software, that will hijack your internet connection and slow things down.

This is brand new Notebook, Just opened & connected to internet. I guess chances of getting any such spyware directly from factory must be very less. Did anayone faced such issue in the past?What hardwar upgrade is recommended for this?

Acer does come with a good amount of bloatware.

yorkspace.com The PC Decrapifier (http://www.yorkspace.com/pc-de-crapifier)

A lot of bloatware keeps an eye on certain things you use, regular software now usually "Send Feed Back" options. Some come with updaters, and web interfaces. All of which will slow your computer down.

Run PC Decrapifier and see if that speeds up your computer. Be careful not to uninstall drivers.