Until recently my mobile phone service provider offered a phonebox service where one could send and receive SMS. This was great for me and even more since I use 2 different computers regularly. With just one computer I could use the Vodafone Connect card but I would need two SIM cards with the same number (impossible). Also, my two computers would need empty PCMCIA slots (can be arranged).
When the mailbox system was scrapped, I had a big problem. First I tried one of the many Internet based services but I soon ran into a problem: since these services are usually USA-based, anybody sending me SMS would be charged overseas rate and any I send would also be charged at a similar rate. Naturally this was unacceptable and very expensive so an alternative solution had to be found.
After an internet search I found MightyText - you install an app on your phone (must be Android...sorry, no iPhone) enter your wifi details in your phone and send/receive SMS from your browser. Particularly useful is the small utility called MightyText Notifier - when I receive an SMS, a popup appears on my screen showing me the number of the sender, the message itself and a window to enter my reply.
Recently I began using Windows 8.1 and had no compatibility issues.
Since I wrote the above, the MightyText Notifier is no longer supported or developed further because now there is the MightyText-Desktop app. It runs at boot and sits quietly until you receive an SMS.