All windows services under Windows Os run for a specific purpose and are essential. But these services don’t run free of cost. Any service that runs on your computer requires space in memory and some processor time. By default there are some services that run and not required by all users. This is not a good idea having these turned on if you are not using them and especially if you are low at RAM (say 256 or even less). So it’s better to turn off them. Disabling the useless services will free up some amount of RAM for other applications and for security purpose also. Here I have compiled a list of services that can be disabled without affecting your normal working. Please note that these simple tweaks are most suitable for home users. (If you are using your system at office and have all those server and intranet setup, please stop here.)
Let’s go to services panel, go to Start -> Run -> and type "services.msc" and hit Enter.
Computer Browser
What it does: Maintains an updated list of computers on the network and supplies this list to computers designated as browsers.
This service can be disabled without any issue. Disabling this service still allows you surf internet and connect to a network.
Distributed Link Tracking Client
What is does: Maintains links between NTFS files within a computer or across computers in a network domain.
This service allows you to create a shortcut to a file residing on a different computer under a network. Most users (home or office) don’t use this often. Moreover this requires NTFS file system which is not used by all users.
Error Reporting Service
What it does: Allows error reporting for services and applications running in non-standard environments.
When computer encounter some error it sends an error report with system information to the Microsoft. Simply disable it.
Help and Support
What it does: Enables Help and Support Center to run on the computer.
Windows provide a help feature by hitting F1 key. If you are not one of those who are not using feature frequently, disabling this service would be good idea.
Indexing Service
What it does: Indexes contents and properties of files on local and remote computers; provides rapid access to files through flexible querying language
This service is responsible for indexing the files on you hard drive for frequent searching. If you are using other searching softwares like Google Desktop search, having this turned on is not a good option. Disable it.
Net Logon
What it does: Supports pass-through authentication of account logon events for computers in a domain.
Home users can disable it as they are generally not in a network and even office users don’t require it frequently.
NetMeeting Remote Desktop Sharing
What it does: Enables an authorized user to access this computer remotely by using NetMeeting over a corporate intranet.
As said above description. It is used for internet meeting when you want to expose your desktop to the remote user. Ask yourself, do you really need this. No? Why don’t disable it.
Network Location Awareness (NLA)
What it does: Collects and stores network configuration and location information, and notifies applications when this information changes.
I don’t think you need this. Go disable it.
TCP/IP NetBIOS Helper
What it does: Enables support for NetBIOS over TCP/IP (NetBT) service and NetBIOS name resolution.
You won’t find it useful. Disable this.
Themes
What it does: Provides user experience theme management.
Many users like the classic interface (old style) of windows. Disable this only if you don’t want to use the cool themes of Windows XP (Default Blue/Silver/Green).
Uninterruptible Power Supply
What it does: Manages an uninterruptible power supply (UPS) connected to the computer.
There is no reason to enable this service if you don’t have a UPS that have automatic turn off feature (independent of computer). You can disable it.
WebClient
What it does: Enables Windows-based programs to create, access, and modify Internet-based files.
It’s a perfect crapshoot. Disable it.
Server
What is does: Supports file, print, and named-pipe sharing over the network for this computer.
Require only if you want to share the file and printer over a network. Disabling this wouldn’t disable the simple file sharing. It’s a good idea if a home user disables this.
Smart Card
What it does: Manages access to smart cards read by this computer.
Are you using Smart Cards with your computer? If no, disable this.
SSDP Discovery Service
What it does: Enables discovery of UPnP devices on your home network.
UPnP are external devices that are a part of intranet. Here you don’t need to confuse it with PnP devices. Disabling this would affect your PnP devices.
Remote Desktop Help Session Manager
What it does: Manages and controls Remote Assistance.
Nah! I personally wouldn’t recommend enabling Remote Assistance for security reason. You should disable this service.
Remote Registry
What it does: Enables remote users to modify registry settings on this computer.
Are you Crazy? Disable this without further questions. 
Please mind you that the above list is set of settings that I have been using on my home computer for past few months. Luckily or whatsoever, I have not faced any problem till now. In fact, I am happy with the kind of performance I am having on my system. I am usually one of those who always wanted to have information what is running on my system at a given point of time and Why? Disabling the useless services not only save you extra chunk of memory but also good for security purpose. The above compiled list is totally based on my personal experience and I recommend it for other users like me. At last, if you are not ready to troubleshoot problem you are probably not the one who should try it.
Happy tweaking!