Should I pay up to get my files back if my computer is infected with ransomware such WannaCry - also known as "Wanna Decryptor" or "Wanna Crypt"?
It's best not to.
If you have recent backups of your data and have no critical files at risk then the safest thing to do is reformat your system and to reinstall Windows and restore your files from a backup (after ensuring your new Windows system is up to date with software patches and installing an AntiVirus package).
Some of the versions of malware have "backdoors" which can be used to disable them. Kaspersky and Trend Micro provide tools which can help you decrypt your data for free and protect your computer against future attack.
Those who have been subject to ransomware in the past and have paid up have reported mixed results. There have been high profile cases, with one hospital paying up to $17,000 where victims did report getting their data back after paying up.
However there is no guarantee you will get anything back and there is no way to hold the ransomers to account if they don't. By paying up you may also be encouraging more ransom attacks.