Xampp version:1.7.7 (installed it on external hard drive), operating system: Windows 8, installed version 4.1.7 of phpMyAdmin and copied config.inc.php from my old version
did you try 'localhost/phpmyadmin' ? (notice the lowercase)
PHPMyAdmin tends to have inconsistent directory names across its versions/distributions.
Edit: Confirm the URL by checking the name of the root folder!
If the config was the primary issue (and it may still be nthary) you would get a php error, not a http "Object not found" error,
As for the config error, here are some steps to correct it:
Once you have confirmed which case your PHPMyAdmin is in, confirm that your config.inc.php is located in its root directory.
If it is, rename it to something else as a backup. Then copy the config.sample.inc.php (in the same directory) and rename it to config.inc.php
Check if it works.
If its does, then open up both the new config.inc.php (that works) and the backup you took earlier of your old one. Compare them and copy/replace the important parts that you want to carry over, the file (in its default state) isn't that long and it should be relatively easy to do so.
N.B. If the reason that you want your old config is because of security setup that you once had, I would definitely suggest still using the security wizard built into XAMPP so that you can be assured that you have the right configuration for the right version. There is no guarantee that different XAMPP/PHPMyAdmin versions implement security/anything in the same way.
XAMPP Security Wizard
http://localhost/security/xamppsecurity.php