Try this:

Open your Users Library folder and find the files that you would wish to delete. Select one of the files and either press Command-I or go to File>Get Info. The Get Info window will tell you who owns the file if you look under Sharing & Permissions (you may have to click the triangle to expand it).

In order for you to be able to delete the file, your account should have Read & Write privileges. If not, you can change it via the double arrows alongside it. If it is grayed out, click the padlock icon and enter your administrator password when prompted. Then, you should be able to change the privileges and delete the file. Do the same for the other files, if necessary.

I am writing this based upon my Snow Leopard installation. Some of the terms may have been slightly changed in Lion so be prepared for that.

Jon

macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365