Delete "old" Windows files under C:?

I've had two Win 7 crashes that required clean reinstalls. I see two entries under C: - Windows.old.000 and Windows.old.001. My last crash reinstall was about two weeks ago. The old.00 only shows 1.39MB, the System32 file is empty; the old.001 takes up. 18.3G and has all System 32 stuff.
Is it safe to delete old.001 that takes up so much space? And, since the old.00 is almost empty, is it OK to delete that also?
I have Acronis True Image backups, Windows backups and Carbonite. Thanks very much for your ideas. ec

Ahh that pesky Windows.old...

That file gave me a hell of a time when I went to remove it. The best way to get rid of Windows.old (and I wish I knew this back when) is as follows:

Click on Start/All Programs/Accessories/System Tools/Disc Cleanup

When the dialogue box pops up, select the appropriate drive and click OK. The system will do a quick scan and another dialogue box will open. At the bottom left, click Clean up system files.

You'll see another scan like the first one, and then another similar looking dialogue box appears. This time, though, there will be a check-box in the list called Older Versions of Windows. Click it, and click OK. The Disc Cleanup utility will do the rest.

Those files/folders indicate that you have performed an upgrade rather than a full, clean install of Windows 7. Be aware this may present problems for you in the future. A clean install is always preferred. A full, clean install leaves NOTHING behind.