Concept:
Computer memory measurements are based on powers of two because computers operate using the binary number system.
Step 1: Recall the hierarchy of memory units.
Memory units increase in the following order:
\[
\text{Byte} \rightarrow \text{Kilobyte} \rightarrow \text{Megabyte} \rightarrow \text{Gigabyte}
\]
Step 2: Use the standard binary conversion.
In computer memory:
\[
1 \text{ KB} = 1024 \text{ Bytes}
\]
\[
1 \text{ MB} = 1024 \text{ KB}
\]
\[
1 \text{ GB} = 1024 \text{ MB}
\]
Step 3: Determine the value of one Gigabyte.
Since one Gigabyte contains 1024 Megabytes,
\[
1 \text{ GB} = 1024 \text{ MB}
\]
Step 4: Choose the correct option.
Therefore,
\[
\boxed{1024 \text{ megabytes}}
\]
is the correct answer.