if i restore my c: drive on my sony vaio will it delete the windows operating system?

If you use the "System Restore" feature in windows then it will not uninstall the windows operating system but will uninstall any windows updates that have installed since the restore point you choose to use. it will also revert any system files and setting and changes in the registry to the date the restore point was made but not affect your personal files in any way.

To remove the windows operating system completely you will need to reformat the drive it is installed on. A format will delete all ssystem files, insatlled programs as well as any personal files on the same disk/partition.

if you are talking about using a "Restore Disk" or you have a "Restore Partition" on your hard drive [provided by an OEM manufacturer] then using this will reset the computer back to factory settings. So you will still have a basic windows system but all the software you have installed and all your personal files will be removed. The system will be put back into the state it left the factory when new.

system restore just restores back to an earlier day, like example 5 days ago when everything might have been working better. start/all programs/accessories/system tools/system restore. You will not lose any docs or pics. You will however lose any programs you have installed in the last 5 days.

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next there is system recovery, if you didn't get or make recovery disks you might be able to revover from your D drive. You will lose all programs you have installed and pics and docs.

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Next you can format your hard drive , but you will need to have the OS disk. Formatting deletes everyhting.

What type of restore? If its a restore to an earlier c than you are fine. Restoring to factory settings may wipe it all

You may use Windows System restore to restore your computer to an earlier time, otherwise there is another good practice to create backup of your C drive with your desired settings, you can use Drive Image to create backup and restore it whenever your operating system crashes or slows down.

If you completely erase it then yes if you restore it to a previous time then no.

You don't really know what restore means ,aren't you