Обновите Windows 7 до Windows 8.1, что-то может пойти не так?

Generally, there should be no problems with the upgrade.

Some potential issues are:

1. Hardware issues

This can be solved by downloading drivers either from Windows Update, or your manufacterer's website. For example, I have an Acer laptop so I go to Acer Downloads to get my drivers if they weren't detected in Windows Update.

2. Driver issues

During installation, but not likey after it.

3. OneDrive(formerly SkyDrive)

If you use OneDrive then you might notice that some files synced will be "Online-Only". If you want to download it, then just right-click, "Make Available Offline".

However since you've been running Windows 8.1 for a while, then the issues would most probably be non-existent. The most likely time to run into problems is during the Upgrade.

Whether it will be just like it was installed freshly on an empty partition, well the system files yes, but your personal files no! :P

After some time, you'll get used to and love Windows 8.1 like I did! :)

Read more here.

Being a perfectionist for a Windows upgrade is setting yourself up for a great fall. The only way that I think this can be done with little or no problems is to have the installation disks/downloads for every piece of software you want in your new system, then perform an 'Easy Transfer' from Windows 7. You then install a new, clean Windows 8.1 system, reinstalling the software you require (assuming that everything that you want is windows 8.1 compliant), then performing the 'windows easy transfer' back to your new 8.1 system.

Upgrading always seems to create more problems along the lines of sluggish performance, driver errors, odd freezes, etc.

Unless there is a system on the machine which is a pig to reinstall or cannot be reinstalled which is critical to your business - I wouldn't upgrade but just backup and start afresh using the method above.

I once had to upgrade a shops till system from Xp to Window 7. I had to upgrade as the till software company had gone bankrupt and were no longer trading, and the costs of transferring to another system were so astronomical that the only solution they had was to keep using what they already had. It took a very long time, had a myriad of problems, and ran so badly only the addition of an SSD could make the computer useable.

Upgrading always leaves portions of the old system behind and always makes the system registry huge, and therefore difficult to work with.