I'd say to run MBAM too (Malwarebytes Anti-Malware). Perhaps also JRT (Junkware Removal Tool) and/or AdwCleaner. Will they cause any harm? It can't be guaranteed that they won't. Some cleaning programs might cause harm if malware is deep seated enough. If a system file has been corrupted and a cleaning program finds and removes one of these, this may become a slippery slope that leads to formatting and reinstalling anyway.
Since your friend has paid to have the computer cleaned, it is possible that the computer repairer has already tried quite a few cleaning tools, including the ones mentioned. If this is the case, he is probably right in saying that the situation is as good as it is going to get without reinstalling the operating system and programs.
I'd say the best course is to buy an external USB drive, copy any created files to it (photos, written documents for instance). At least then these files won't be lost no matter what happens This should be done as a matter of course right now anyway, as already suggested. Having done that, go for the re-installation of everything. Before putting the backed up files onto the re-installed system, scan them with an AV program.
Flopsymopsy has suggested ways of preventing problems of this nature. My only addition to what has already been said is to back-up. Not only photos and other created files but also make a back-up of the entire
working system. Such a back-up is called a 'disk image'. A disk image usually takes the form of one large file that contains the operating system, installed programs and all created files (photos, documents etc.). The disk image can be written to a USB external drive and used to recover the working system if it ever gets infected, corrupted or somehow messed up.
Writing back a saved disk image to the computer takes about 30 minutes compared to the day or more it might take to reinstall the OS and programs. What's more, it does this without having to think about what to do. All that has to be learned is how to make the disk image and how to initiate writing it back to the C: drive if it becomes necessary. When this is done, the computer and programs are ready to use without further work (other than letting any Windows Updates install).
Windows 7 includes its own disk imaging program. Instructions on usage here
(scroll down to the 'Here's How' heading). There are some popular third-party programs that will do the job too. These include Acronis, Macrium Reflect and EaseUS ToDo. Free versions of Macrium and EaseUS are available.
The only thing to remember to do when one of these programs is installed is to make a startup disk. If the computer becomes so bad that it won't start, the disk can be used to start the computer up, access the disk image on the USB drive and initiate the recovery process.
This might seem a complicated procedure but it is the simplest and quickest way of getting back to a pristine system if anything goes wrong. The time to make a disk image might be when a computer is new or when the operating system and regularly used programs have been newly installed.