Will my computer slow down if I install multiple operating systems?

It depends on how you install the multiple operating systems – there are generally two options

• installing for dual boot
• installing using a VM

Dual boot installation just places the other OS on free space on your hard disk, so it will use hard disk space (you may need/be-asked-to to create new partitions), but since in a dual boot only one OS will run at any given time, then no memory or CPU is being used by the other OS.

Virtual machine (VM) is a software program which emulates the hardware of a PC. If you use a VM to install your second OS, then both OS can run at the same time – so you can have a Windows PC which has Linux running in a VM-window, and you can use both at the same time. Since you can use both at the same time, they both will use memory and CPU, and then you may see the computer slowing down.

If you don't know anything about how to use a VM, then it is unlikely that you have one, but rather that you have a dual boot system, in which case – NO, you will not see the system slowing down.

The OS you are running will not slow down. Only the hard disk capacity will be decreased.

Theoretically your OS may slow down if you have a running program in the background which scans files on hard disk, because this program will scan all files from all operating system. But this is just a theoretical slowdown which you will not notice.

If you plan to have different OSs in your hard disk (Windows, Linux, MacOS), then Windows OS will not see them and will not be slowed down at all.

You may also consider having virtual OSs via VirtualBox. Myself, for example, have more than 10 OSs and 1 main OS. When I need, let's say, Win 7 for design, I start its virtual machine and have one system running inside other system. I have 8 GB of RAM and I give 4GB RAM to each system and the virtual OS is not slow at all. Just to mention that these virtual OSs are not suitable for gaming.

No: As long as the OS' are installed on dedicated partitions/disks they will not affect the speed of each other.

Yes: There are factors that will cause an OS to go slower. If the partition contains many files (say you install both OS on the same partition (really not recommended as files will conflict)). Another more likely factor is that the first partition (and the first file) is stored on the outmost rings of the disk, so the HD head needs to move less (bigger cirles, more data per cirle). Any files/partition further in will get increasing head moves vs bytes read. So if the second operating system is for example 50% out on the disk the speed will be slightly lower. But it should be said that due to various reasons such as cylinder scew and caching this is not noticeable.

So the answer is: No. The operating systems will not be noticeable slower.

As others have already pointed out running OS as virtual guests will slow down both host and guest OS.

Best advice; Make sure you have plenty of RAM in host OS. The lack of plenty of RAM makes your computer SLOW. I myself run Win7 with 8GB (desktop) and 12GB (laptop) and I've just placed an order for 16GB for my desktop. That is a bit over the top for most users, but benificial for my use.

Installing more than one OS will not slow your computer because they are stored on the hard disk. When you turn on the PC only one OS will be running at a given time.

The computer speed may be slow due to shortage of RAM. In my opinion if you have 2GB of RAM then you can run any OS smoothly.