Need to find a decent priced desktop computer with these requirements?

I'm looking for a desktop computer that can run at least minecraft multiplayer, Skype, and video record at the same time. Without much fps drop.

A laptop that can run steam with video recording and skype at the same time too on games such as garrys mod or GTA 4 and run it quite smooth.

Any suggestions will be a lot of help!
P.S. My budget is around $400 to $500

You have really hit a block with all those requirements. No computer, at that price, will amaze you completely. I advise you look at the Toshiba Satellite. Yes, there are a plethora of models, but the more you can spend, the better it will be. I suggest the newer versions. I normally get 90-100fps running on Eco mode ( A.k.a. Low performance. ) with two USB 3.0 and one USB 2.0 it will be compatible with any current USB plugin device.

Depends where you live. Try gumtree.com instead of an Ebay.

CPU: AMD Athlon II X4 750K 3.4GHz Quad-Core Processor ($79.98 @ OutletPC)
Motherboard: Asus A55BM-E Micro ATX FM2+ Motherboard ($39.99 @ Microcenter)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-2133 Memory ($69.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: MSI Radeon R7 260X 2GB Video Card ($132.98 @ Newegg)
Case: NZXT Source 210 Elite (Black) ATX Mid Tower Case ($42.98 @ Best Buy)
Power Supply: Corsair CX 430W 80+ Bronze Certified Semi-Modular ATX Power Supply ($37.99 @ Microcenter)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($84.99 @ NCIX US)
Total: $548.88
This is a little more because it is amazing quality and includes the OS which most people will leave out since they will probably pirate it. This could max out minecraft with 300+ fps and some modern games like Bioshock Infinite and is very upgradeable.

Here's what I did with your budget:

Desktop:
AMD A10-5800K Trinity 129.99
MSI FM2-A75MA-E35 Micro ATX MoBo 59.79
G.Skill Ripjaws series 8BG DDR3 1066 MHz RAM 79.99
Refurbished: Western Digital WD5000AAKX-FR 7200 RPM 500GB HDD 89.99 (45.00 instant savings)
Diablotek CPA-8821 ATX Mid Tower 45.99 (21.00 Instant Savings)
SeaSonic SS-350ET Bronze certified 350W ATX12V PSU 44.99 (5.00 Instant Savings)

Total cost w/o shipping: 379.74 (if you wanted a good video card I'd plan on spending around $100-120, however the processor I chose has a built-in GPU)
Notice I skipped on the DVD drive and was only able to build a tower, there are no peripherals (keyboard, mouse, speakers, monitor, etc.), so hope you weren't looking for those too. I had to be skimpy on some parts and even then barely came in under $400 not counting shipping or the optional graphics card. $500 can build you a mid-grade tower and it might be able to do all that you want semi-smoothly but I wouldn't count on it running spectacular while recording and playing.

To sum things up, you'd be better off saving that $400-500 until it becomes $800-1,000, then you could build a really top-notch computer and not have to worry about losing any amount of performance. You might even be able to afford your input and output devices (keyboard speakers mouse monitor).

Your not gonna get a laptop at 500 dollars that will run Gta 4 smooth. Gta 4 is not a well optimized game anyway. It even runs poorly on high end systems.