Will I still have my iphone backup if I restore my laptop?

I need to restore my laptop because it has a buttload of viruses on it. I'm moving my important documents onto a 500gb flashdrive before I restore it but when it's restored will my iphone remain the same after syncing it or will it lose it's backup?

Err hard one to give definite answer to.
Back ups normally have an address path within the file systems they store and that is normally linked with the backup program which is used to run them.
OK so if you restore your system then the file address for your backup will be deleted and therefore your backup will not see the required file addresses and so NOT run.
Now your iphone will need to be resynced to the computer which at that time create a fresh new clean backup of your iphones system and files.
Your phone will be the same but the backup will be as the new sync not the same as the old which I doubt it will read.