You have a few options.
1. ASEBA PC 2015 requires at least Windows 7. It can be only be run on a single machine per license, though multiple people can use that machine. Licenses are sold by age group, but there is also a full-set option that gives you access to all age groups.
2. ASEBA Web works on a system of e-units. Each form you send out costs two e-units, and you can see the price of additional e-units here:
The primary advantage of ASEBA Web is that it provides informants access to a site where they can fill out the forms themselves. This may save you considerable time and avoid data entry errors since you won't have to key-enter the forms one by one.
Another advantage is that you can access ASEBA Web from any device including Macs, PCs, and tablets.
Additionally, ASEBA Web is that it gives you access to form protocols from all age groups.
3. ASEBA Network runs on a server on your network. Multiple people can then access it simultaneously from any computer with a modern, up-to-date web browser. Similar to ASEBA PC, you have to buy access to specific age groups or purchase a "full set" license. You can see the installation requirements here: http://aseba-network.aseba.org/