doogiePIM will run on a variety of computers, from laptops to desktops. You don't need a huge beefy machine but it does help to have some good processing power and storage. Especially for when you're collecting data such as lots of images inside journals and documents.
For the operating system you need Window 7, 8.1, 8 or even better, Windows 10. Although many people scoff at Windows 10, its actually a really good system. If you get the Pro version then you have more privacy switches you can play with. Not to mention all the important latest patches from Microsoft to keep your machine safe from harm.
I would suggest you get at least an i5 2GHz processor with an SSD. Also ensure you get USB type 2 or 3 ports to make backups quick and easy. The size of the screen should be at least 1000x600 pixels resolution. Larger is, of course, better.
What a Selection
I've taken a look at some of the machines at Amazon and using their search filter made a quick list. Check it out here.
Amazon laptops suitable for doogiePIM
Of course, use this only as a basic guide and use your own judgement as to what to buy.
I hope this helps. Feel free to comment what kind of machine works for you.