Okay, your PSU is enough for overclocking. Your motherboard is not so reliable, since it's ASRock, however provided you didn't get a defective unit, you should be fine.
The CPU is running pretty hot at the moment, I would NOT recommend overclocking your system as is. 75c is the magic number for Phenom II processors. Passing that voids your warranty, and in all probability will fry your CPU.
Now you need to get an after-market cooler/hs, for around $30~ you can get a neat one.
Once you get the cooler/hs, you should focus on overclocking!
PLEASE READ YOUR PROCESSORS SPECIFICATIONS (Maximum temperature, voltages, and warranty<- void most of the times by overclocking)
That processor could probably be pushed to around 2.8ghz-3.2 ghz depending on the voltage/clock efficiency. You could run into issues with the multipliers being locked, but -shrugs- we'll see.
As far as overclocking safety goes, as long as the voltages remain IN THE MARGINAL VOLTAGES ALLOWED BY YOUR MANUFACTURER your processor should last you the same amount of time. Temperature is also a factor, however as long as it doesn't hit 55c or higher, you should be fine.
Guide for overclocking ONCE you get a after-market cooler, and read the manuals for the CPU:
When your computer boots, you will presented with a BIOS screen, please hit the according key to enter "setup".
Once there, depending on your make and model of your BIOS you will need to look for Advanced Motherboard (or Chipset) settings. Or something verbally along those lines.
From there, once again depending on your BIOS, you should see things such as "CPU Overclocking" "CPU Voltages" "CPU Setup (and or Config)" "CPU NBVolt" "CPU Bus speed" whatever.
What your looking for is the CPU multiplier, as well as the CPU voltage controls. If these two are not supported by your CPU, and or BIOS you will need to look for the Bus speed control and change that accordingly (it is more reliable to use bus speed, however due to the direct affiliation with your RAM you could be subject to limitations by the RAM since you will be in effect overclocking your RAM as well)
The voltage SHOULD NOT GO ABOVE 1.5v!!! Temperatures should remain UNDER 55c with full load!
For CPU multiplier, make small increments of .5x, test the setup using Prime95 (automatic Torture test). If it runs stable for at least 10 minutes, go ahead and raise the multiplier by .5x (keep TEMPERATURE IN CHECK). If one time you increase multiplier by .5x and the setup shuts down all of the sudden you can increase the voltage by around .025~ and keep testing that way until you reach your desired GHz or until your CPU cant stop restarting (make sure you DONT go over 1.5v for the voltage)
Please understand that I am NOT liable for you frying your CPU.
If your PC no longer restarts, it could be because there isnt enough voltage going to the CPu for the Clock speed (or Ghz). In which case you need to "restart" the BIOS, also called removing the CMOS battery. You can google that easily. This will refresh your BIOS to default, putting all CPU settings back to stock condition.
If even after you "restart" the BIOS, your PC won't start. Congratulation you went over 1.5v, or 75c in temperature, after I told you not to and you probably fried your CPU (and in probability damaged some other component).
For Bus speed overclocking, I am afraid I am not too knowledgeable on the subject and would recommend you seek further assistance.