Hello! I'm new here! I have a desktop pc with Win 7 on it. I want to tried Mac. How do I do it? Can it be form a external hard drive?

Hello!!! Is the specs of my pc:

HP G5330pt Desktop PC Product Specifications
Motherboard
MS-7613 (Iona-GL8E)
• Manufacturer: MSI
• Form factor: micro ATX - 24.4 cm (9.6 inches) x 24.4 cm (9.6 inches)
• Chipset: Intel H57 Express
• Memory sockets: 4 x DDR3
• Front side bus speeds: 2.5 GT/s DMI
• Processor socket: LGA1156
• Expansion Slots:
o 1 PCI Express x16 slot for graphics card
o 3 PCI Express x1 slots
o 1 PCI Express x1 minicard slot
• For more details, see Iona motherboard specifications .
Processor
Intel Core i3 550
• Operating speed: Up to 3.2 GHz
• Number of cores: 2
• Socket: 1156
• Bus speed: DMI (Direct Media Interface) - 2.5 GT/s
Processor upgrade information
Motherboard supports the following processor upgrades:
• Intel Core i7-8xx (Lynnfield core)
• Intel Core i5-7xx (Lynnfield core)
• Intel Core i5-6xx (Clarkdale core)
• Intel Core i3-5xx (Clarkdale core)
NOTE: Maximum processor core frequency <= 2.93GHz
Memory
4 GB
• Amount: 4 GB
• Speed: PC3-10600 MB/sec (messages as PC3-8500)
Memory upgrade information
Memory upgrade information:
• Supports DDR3 DIMMs only
• Dual channel memory architecture
• Four DDR3 DIMM (240-pin) sockets
• DIMM types:
o PC3-10600 (DDR3-1333)
o PC3-8500 (DDR3-1066)
• Non-ECC memory only, unbuffered
• Supports up to 16 GB on 64-bit PCs
• Maximum memory only if using 4GB DDR3 DIMM modules.

Video graphics
AMD Radeon HD 6450
• Interface: PCI Express x16
• 1 GB onboard memory
Integrated Intel H57
*Integrated video is not available if a graphics card is installed.
• Integrated graphics using Intel H57 chipset (when compatible CPU is installed)
• Intel HD Graphics
Sound/Audio
Integrated Realtek ALC888S Audio
Integrated High Definition audio
• Audio CODEC: ALC888S
• 6-channel high-definition audio
• AC97: no
Networking
LAN: Gigabit 10-Base-GT
• Technology: Realtek RTL8111DL 10/100 Mbps
• Data transfer speeds: up to 10/100/1000 Mbps
• Transmission standards: Gigabit 10-Base-GT Ethernet
Hard drive
1 TB
• Size: 1 TB
• Interface: SATA
• Transfer rating: 3.0 Gb/sec
• Rotational Speed: 7200 RPM