Yes, it is safe to delete the quarantined files. As to cleaning up the olddrive folder, use the Disk Cleanup tool which helps you free up space on your hard disk by searching your disk for files that you can safely delete. You can choose to delete some or all of the files. It can also be used to clear all but the most recent System Restore point.
First, create a fresh restore point:
1. Click Start, click All Programs, click Accessories, click System Tools, and then click System Restore.
2. Click Create a Restore Point, and then click Next.
3. Name your restore point. (i.e., clean)
4. Click the Create button.
5. When the new restore point has been created, click Close.
Now select the files to be removed as well as all but the new restore points:
- Click start-->Run and type cleanmgr into the run box and then click "OK".
- Select the drive where Windows is installed (if you have more than one drive) and click "OK".
- When the scan completes, check/uncheck desired boxes.
- Next, please click the More Options tab at the top.
- Click the "Clean up..." button under the System Restore section at the bottom.
- Answer Yes to the question "Are you sure you want to delete all but the most recent restore point?".
- Click OK and answer Yes again.
The disk clean up utility will remove the selected items. When it completes, please restart the computer to properly record the changes made to the hard disk.