No, the only you can do online is order a disk.
If you have Vista currently: Open System Restore by clicking the Start button Picture of the Start button, clicking All Programs, clicking Accessories, clicking System Tools, and then clicking System Restore.
If you have XP: Click Start, click Control Panel, click Performance and Maintenance, and then click System. In the System Properties dialog box, on the System Restore tab, use the slider to increase the allocated disk space, and then click OK.
If you have an HP computer:From the Windows XP desktop, click Start, All Programs, and then HP Tools. Select HP PC System Recovery. The Recovery screen will appear with the question Do you really want to start HP PC System Recovery? Click Yes, to continue the recovery process. When the Recovery screen appears, click Next, and then click Yes to perform a normal, non-destructive recovery.
All of these options will completely erase everything you have on your computer except for the files it came with D: So...if you had XP and upgraded to Vista, you'll only have XP again. I recently had to start from scratch because I broke my own computer and I'm really not missing the majority of files I lost XD; Just make sure you backup the files you need.