What does it cost to register a domain?
Typically domain name prices range in the $9 to $10/year range for .com, .net, .org domain, which are the most common formats.
Each registrar sets there own prices, so look around to find one at a good price.
What if someobody else registered my company name?
If you own the trademark to your company name, you may be able toget it back by filing a case with ICANN Domain Resolution. There is a fee for doing this. However, most often you may find that you cannot do anything about this, in which case you should look for alternative in other TLD's such as .net, .us or .biz.
What is a TLD?
TLD (or Top Level Domain) is basically the domain extension such as .com, .net, .de, .am, etc.