Unable to free up enough space (1.5 GB at least) on your hard drive.
at least 也可换成 minimum.不过一般都不这样说,而是分开成两句话:
The minimum hard disk requirement is 1.5 GB.xxxx is unable to free up enough space on your hard drive (或者 on hard dirve C:)
这里的xxxx是某个程序或应用的名词.