Hi I want to share my DSL internet connection with 2 more PCs (inside my home, one has windows and 1 has linux). Which is more recommended; a router or a switch? What are their pros and cons? Thanks

A router is what you need. There are no pros or cons except that switch by itself wont work. Stuart

What do mean by "switch itself itself wont work"?

Unless you have 2 Internet Public IP for your DSL Internet connection, you can't share Internet connection with 2 PCs. That's why you need to get a router to build a simple and share Internet connection. You can either get a wired Ethernet router or wireless router to build a network. Here is simple wireless network and wired Ethernet network setup tutorial, you will get more ideas after the reading.

A switch is for connecting computers together in a Local Area Network. A router is for connecting two networks together, in this case your Local Area Notwork and the Internet. Most home routers come with s switch built in. A switch by itself won't do multiple connections to the Internet unless as picochat says you have multiple public IP addresses. You can have as many private IP addresses on your LAN as you want but public IP addresses are allocated by your ISP. Stuart

After adding router to my network and plugging my PCs by a CAT cable, what setup I have to run in Windows to enable internet? Also which type of CAT cable should I use (which can give me maximum performance)? Also which type of Cable whether cross cable or some else I use?

The manual for the router will tell you all this. There is no point in detailing them here as each manufactures is different. Barically you connect to the router via a web interface and take ot from there. The only question that van be answered is the you need Cat5 patch cable, no crossover. This will almost certainly come with the router as well as the instructions. Stuart