I have 7 computers connected to a network but without a server PC. Want to configure one computer to act as a server so that all the other computers connects to the internet though the Server. Currently all of them are connected directly to a router. How can I achieve this
Servers don't usually act as a network gateway, servers are typically used to serve files to computers on the network or assign privileges for PCs on the network.
I'm not sure why you want to do this and what purpose you expect to gain from this setup. At the end of the day a router/server/PC are all the same but each hardware is specified to work best at specific task.
All I want is to have all the other computers connect to the internet though a server pc. In short what I want to achieve is just to install internet security in one computer and then allow the rest to access internet though the computer where antivirus is installed
That's really not a good security strategy because you would be running a software based firewall. It's better to have a dedicated firewall or a router, which almost all include basic firewall features.
I think you are also confusing anti-virus with firewalls, you still need an anti-virus program on all of your computers, there's no way getting around that. It's also good to keep your PC's firewall active as another layer of protection behind your router's firewall, (the included Windows Firewall is fine).
If you are trying to save costs by only buying one security software license forget it, what you are trying to do is not secure and won't work. Antivirus needs to be actively running on each PC for it to be effective against viruses. There are high end security appliances that can scan for viruses on the network, but these are expensive and still do not negate the need for antivirus software on each individual PC.
I'm not really familiar with this but it seems to now be 64 bit only, or at least the 32 bit version is difficult to find. If your PC is 64 bit I'd go with that and maybe even add some memory, if it's 32 bit look for the 32 bit version.
The major achievement I want is actually to have the other computers disconnected from the internet as long as the server is off. And a way that I can restrick some comps from accessing internet. Currently I have a harddisk which cant boot because of viruses I believe. Its giving an error that it is corrupted and unreadable. I am troubled because I got som important data there