CPU temperature help ( case fans )

depends on the cpu manufacturer, and computer. For an intel desktop, idleing at 50c isn't a bad thing. for an AMD it is. For a laptop, the answer is NEVER overclock the laptop.

Ok a few things would help - what CPU do you have (Intel or AMD and a model would help) and any details on your case and maybe what motherboard you have as well.

If you want to get into overclocking, replacing the stock cooler with an aftermarket one will be the most effective thing you can do to bring temperatures down. However, if you are on a tight budget or just want a little bit of extra cooling, adding some case fans will help. The case fans will prevent hot air from staying in the case and help bring in cooler outside air - this means that your CPU fan will be getting cooler air and do a bit better of a job keeping your temps down. The gains aren't going to be massive but you should see at least a few degrees of difference.

As for the temperature, 50C is fairly warm (although not uncommon with stock cooling), so you wont be able to overclock much. You should be able to increase the speed by a couple hundred MHz or so even with the stock cooling. Again this all depends on what CPU you have, Intel CPUs often have higher thermal limits than AMD ones so your mileage may vary.

Some great tools to have for overclocking (what I use) are:

CPU-Z (tells you important information about your current CPU, like what model you have, speed, voltage, etc...)
http://www.cpuid.com/softwares/cpu-z.html

HWMonitor (great program for keeping an eye on your temperatures, has CPU, mobo, and graphics temps)
http://www.cpuid.com/softwares/hwmonitor.html

For stress testing (to see if the pc crashes and what the max temps get up to) I like either

Prime 95
http://files.extremeoverclocking.com/file.php?f=205

Intel burn test (very intensive stress testing)
http://www.techspot.com/downloads/4965-intelburntest.html

Just a final note, if you are getting in to overclocking you need to know some very specific information about your CPU. Like, maximum safe temperature and maximum safe voltage. Also make sure you know how to use those programs/what the important parts are before you start.

SHORT ANSWER: Case fans will help a little, getting an aftermarket cooler is most effective though. How much you can do depends on what CPU you have.

Sorry if I have covered a bunch of stuff you already know. If you need any further help just let me know. Happy overclocking!

UPDATE:
Did a quick check online on your CPU and mobo. Apparently the max possible temp before shutdown for your CPU is 100C but people seem to recommend making sure your load temps don't go much above ~70C. Also max voltage is 1.45V I believe.

Here are a couple other people with your CPU and a little bit of basic overclocking stuff. Some of it should be relevant:

http://www.tomshardware.com/forum/258212-29-core2-e7500-overclocking-advice

http://www.overclockers.com/forums/showthread.php?t=619716

http://www.overclockers.com/forums/showthread.php?t=515316

Yep you have an Intel CPU, it was in your screenshot. The model is a Core 2 Duo E7500. The stress test programs are there just to see how hot everything gets when under load so keep an eye on those temperatures when running them. For normal use your CPU wont get as hot as the stress tests will get it.

As for coolers something like the:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835608018#top (high end air cooler, great performance but big)

http://www.newegg.com/Product/Product.aspx?Item=N82E16835181031 (closed loop liquid cooler, very good performance and can be quiet too)

http://www.newegg.com/Product/Product.aspx?Item=N82E16835118223 (affordable, not too massive, decent performance)

I have heard good things about all of those Some are a bit pricey though and can be bulky (make sure you have room in your case), but really anything other than stock cooler does a better job. Now as to me personally I like the closed loop water coolers, good performance and nice and quiet too, but once again maybe a bit spendy. The Corsair H80i (the liquid cooler) is one of my favorites. The other nice bonus of having a better cooler is your system should be quieter when at idle and the electronics last longer at the lower temperatures.

All of those should fit your system as well but it is good to double check before you buy one.