What is claimed is:1. A portable data storage device comprising:a main housing having two end holes formed through two opposite ends of the main housing;two outer side surfaces oppositely defined on the main housing; andtwo pivoting parts formed on the outer side surfaces of the main housing respectively and both located along a first axial line;a data storage module mounted in the main housing and having a first electrical connector and a second electrical connector, and the first electrical connector and the second electrical connector protruding out of the main housing through the two end holes respectively;a first protective swivel being U-shaped and having two inner panels, and each of the inner panels having a first end, and the first ends of the two inner panels connected to each other to form a closed end of the first protective swivel;a second end, and the second ends of the inner panels spaced at an interval such that an opening end of the first protective swivel is formed;an inner surface; andan outer surface;two inner pivot parts formed on the inner surfaces of the two inner panels respectively and pivotally connected with the two pivot parts of the main housing respectively; andtwo outer pivot parts formed on the outer surfaces of the two inner panels respectively and both located along a second axial line, wherein the first axial line passing through the two pivot parts of the main housing does not coincide with the second axial line passing through the two outer pivot parts of the first protective swivel; anda second protective swivel being U-shaped, and having two outer panels, and each of the outer panels having a first end, and the first ends of the outer panels connected to each other to form a closed end of the second protective swivel;a second end, and the second ends of the outer panels spaced at an interval such that an opening end of the second protective swivel is formed; andan inner surface; andtwo pivot parts formed on the inner surfaces of the two outer panels respectively and pivotally connected with the two outer pivot parts of the first protective swivel respectively; andwherein the second protective swivel is driven to move laterally due to the rotation of the first protective swivel.2. The portable data storage device as claimed in claim 1, wherein a first distance defined between each of the outer pivot parts of the first protective swivel and the closed end of the first protective swivel is smaller than a second distance defined between each of the pivot parts of the second protective swivel and the closed end of the second protective swivel.3. The portable data storage device as claimed in claim 2, wherein a third distance defined between each of the inner pivot parts of the first protective swivel and the closed end of the first protective swivel is greater than a fourth distance defined between each of the pivot parts of the main housing and an end surface of the first electrical connector and is also greater than a fifth distance defined between each of the pivot parts of the main housing and an end surface of the second electrical connector.4. The portable data storage device as claimed in claim 2, wherein the first electrical connector and the second electrical connector are different kinds of electrical connectors.5. The portable data storage device as claimed in claim 1, wherein a third distance defined between each of the inner pivot parts of the first protective swivel and the closed end of the first protective swivel is greater than a fourth distance defined between each of the pivot parts of the main housing and an end surface of the first electrical connector and is also greater than a fifth distance defined between each of the pivot parts of the main housing and an end surface of the second electrical connector.6. The portable data storage device as claimed in claim 5, wherein the first electrical connector and the second electrical connector are different kinds of electrical connectors.7. The portable data storage device as claimed in claim 1, wherein the first electrical connector and the second electrical connector are different kinds of electrical connectors.8. The portable data storage device as claimed in claim 1, wherein the first electrical connector and the second electrical connector are different kinds of electrical connectors.