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In this modern era, high tech devices that are very expensive like the computers can be replaced with cheaper ones. Such cheap computers mostly come in the form of used computers. Used computers can be found in abundance in the used computer warehouses in various places, even in the local area of the prospective buyer’s residence. However there is no guarantee of quality when buying a used computer.

The buyer has to take his own personal risk in doing so. But, if the buyer is ready to spend some money in upgrading the level of the used computer and also some time checking the quality of the used computer before purchase, it will save him from loss. Used computers can save a lot of money for the buyer when compared to buying a new computer. There are many who cannot afford to buy a new computer like the students who do not have any source of income but definitely require computers. For such people, used computers come as a boon.

Also, used computers need not always be second hand computers. They can also be recertified or refurbished computers. Refurbished or recertified computers are those, which are checked for any faults, if any corrected and sold with a warranty ensuring the working condition of the computer to be perfect. Hence, such computers are considered to be the safest form of buying a used computer. Refurbished computers can be bought from many of the online stores at very less prices. Quality computer manufacturers also sell such kind of recertified or refurbished computers. However, certain measures need to be taken while buying such kind of computers.

The prime aspect to be considered while purchasing a used or refurbished computer is to look for a good branded one. There are various companies who sell used computers or refurbished computers. The main reasons for opting for a branded one is that it comes with a warranty and also the buyer can be sure that the parts used are of good quality.

While buying used or refurbished computers related software documents, licenses and paperwork have to be got from the seller as this will avoid stolen computers being passed off as used computers to the buyer. If possible working for some time on the used computer will determine its efficiency. Most of the reputed dealers would allow the purchaser to use the computer for a shorter period to check the quality before purchase.

While checking for the efficiency of the used computer, it is good to check if the booting process is smooth, as most of the problems occur during booting and also to check all the sound drivers, video, graphics, monitor, mouse, keyboard etc. CD drives and hard disks also need to be checked. Another aspect is the support system offered for the used computer whether technical or non-technical, support staff capabilities and the number of support staff which determine the quality of service offered. If the purchaser is not satisfied, he can very well think of another choice.

Hamachi is a centrally-managed zero-configuration virtual private network (VPN) freeware application capable of establishing direct links between computers that are behind NAT firewalls without requiring reconfiguration (in most cases); in other words, it establishes a connection over the Internet that very closely emulates the connection that would exist if the computers were connected over a local area network. Currently available as a production version for Microsoft Windows and, as beta, for Mac OS X and Linux.

How It Works

Hamachi is a centrally-managed VPN system, consisting of the server cluster managed by the vendor of the system and the client software, which is installed on end-user computers.

Client software adds a virtual network interface to a computer, and it is used for intercepting outbound as well as injecting inbound VPN traffic. Outbound traffic sent by the operating system to this interface is delivered to the client software, which encrypts and authenticates it and then sends it to the destination VPN peer over a specially initiated UDP connection. Hamachi currently handles tunneling of IP traffic including broadcasts and multicast. The Windows version also recognizes and tunnels IPX traffic.

Each client establishes and maintains a control connection to the server cluster. When the connection is established, the client goes through a login sequence, followed by the discovery process and state synchronization. The login step authenticates the client to the server and vice versa. The discovery is used to determine the topology of client's Internet connection, specifically to detect the presence of NAT and firewall devices on its route to the Internet. The synchronization step brings a client's view of its private networks in sync with other members of these networks.