You can use Reaper.

http://www.reaper.fm/

It is not free but awesome and the cheapest one you can really work with professionally and with full function and ASIO support. After 4 weeks of testing you should be so fair and pay that tiny 60$ to get your private license, although it will continue working without.

If you buy the v4 license, you will also have the future v5 license.

The license is just registered to you, not to the pc. You'll get a license file which can be used for any pc. So you won't have any problems if you buy a new pc or have to reinstall your operation system.