Operating System Update

[CheeseChaser]

If you were to change your operating system on your computer, would all the files and installed programs be deleted?

[Axw_JD]

Yes.

Unless you were doing an in-place upgrade (which you should never, ever do. Its the easiest way to introduce problems to an otherwise perfectly working computer and OS).

If you are going to upgrade, for example installing Windows 8, and you are currently using any other version of Windows, is advisable to make a backup copy of your files, and during the installation tell it to install from scratch, deleting anything you previously had on your hard drive.

[Rayquaza]

It depends on what OS.

In place upgrades (like the user above me said) will upgrade the computer to a newer edition of the operating system. (Though, it doesn't make many problems to be honest, I don't know what the user above me is talking about). In place upgrades are upgrades which are through software such as:
Windows Anytime Upgrade (Upgrade to a more expensive, but better version of Windows)
A Windows Installation Disc ("Upgrade Now" in the prompt when the disc is inserted)
or in Mac OS X; through a download of the OS application.

If you do a clean installation of Windows Vista, 7 or 8 on top of an existing previous Windows Installation, the files from the following:
(Where C:\ is the location of your hard drive)
C:\Windows
C:\Users
C:\Program Files (x86) [if the operating system was 64-bit]
C:\Program Files

Would all be moved to a folder in C:\ in a folder called Windows.old.

These files contain your documents, music, pictures and such. It also includes installed programs installed to that directory (C:\Program Files) and Windows files too. It only moves the files if the previous operating system before was Windows Vista, 7 or 8.

If you erase and partition the hard drive, all data is deleted. This is something that usually must be done for Linux installations as you will have to format the hard drive with and Ext3 or Ext4 file system, whereas with Windows it is formatted with NTFS.

Just in-case, you should always back up your data. If you don't have a memory stick, I'd recommend using an online storage service such as Dropbox, Box or Sugarsync. Each will give you 5GB of storage.

Update: Turns out dropbox gives you 2GB not 5.

[Axw_JD]

in place upgrades, both on Windows and Linux, can leave conflicting programs and drivers that, at best, will take up space on your hard drive, and at worst will cause performance and reliability issues. Is not something that happens all the time, but from my experience, is common enough to suggest avoiding it. Of course this is only talking about in-place upgrades from one version of the OS to the next. Clean installations on the same partition / drive, Windows Anytime Upgrade and incremental updates are not what I call In-Place Upgrades.

Instead of using dropbox (and its mere 2 GB), I would recommend SkyDrive (http://skydrive.live.com). It gives you 7 GB (25 GB if you were an old user) for free, and you can use Windows Live Mesh or the Windows Live SkyDrive apps to sync folders and files automatically (and starting with Windows 8, systems settings and personal configurations too). If you already have a Windows Live ID / Microsoft Account, you already have SkyDrive.

[Mirage]

Well there are technically two different types of reinstall. One is an upgrade and the other is a clean install.

An upgrade can only be performed from Windows Vista to Windows 7 and it preserves all files and settings. Note however that it does not preserve your programs and all programs must be reinstalled. A clean install is just that, a clean install. Everything is wiped and the new operating system is installed.

Hope I helped :)

[Silicate Wielder]

unless you are doing system updates or have backed up your files to a FD or EHDD yes you will lose all your files

FD = Flash Drive

EHDD= External Hard Disk Drive

[thetechguy2]

No, and Yes.

If you perform what is called a clean install, which is what almost all upgrades do by default, then YES. It does what it says on the tin. It cleans everything.
All your data is gone, it is a new PC again.

If you do an Upgrade, NORMALLY your files and settings are saved.

ALWAYS good to do a backup before upgrading.

Hope this helps.