. . . only if you have a backup-*.iwzip-file to import the project . . .

You need the backup file, as Pcssa suggests. That's why it's so important to have your computer backed up regularly, either to an external disk or the Cloud. If you have done this, you should be able to find .iwzip files on your backup and you can use these to import your site back into X5.

If you don't have these there is no way to get your site into X5 from the published version on the internet other than to copy and paste it back into a new template. This is time consuming but quicker than starting from completely new!

I recommend a Cloud service like GotBackup? (see my site for details) which works away in the background backing up your files, uses little resources and is easily accessible after a crash.

Sir I want to purchase website x5 professional but i have a doubt,If i Purchased it and my motherboard crashed will i be able to install it in another pc

. . . if you are a registered user all licences you can find in your profile - as well as the serials and the downloads of the last version . . .