First, you have to get the MD5 checksums of the files you uploaded:
1. Log into your Google Drive account.
3. Scroll down to the Try it! section.
4. Change "Authorize requests using OAuth 2.0" from OFF to ON by clicking on it, then select:
and click Authorize.
5. Choose your account then click Accept.
6. Fill in the fields field with:
to only get a list of filenames and MD5 checksums.
7. Click Execute and you'll open a list with all the files uploaded to Google Drive and their MD5 checksums.
Now you have to get the MD5 checksums of the files on your hard drive and check them against the values in the list provided by Google Drive. I use WinMD5 for that, a free application perfect for the job.