Should I return a HP p2-1310 Desktop & build something?

In terms of value, you will almost always do better with performance by building your own. The thing is you will most likely need to go back a generation in hardware or find a very slick deal to make a complete PC for the same price as the HP.

The HP is ok for an entry level machine, but the processor is mediocre at best.. See where it stands :
http://www.cpubenchmark.net/cpu_l...APU&id=251

My advice would be to set a budget and buy the best hardware you can afford. For $250 right now you can get this:
http://www.frys.com/product/74155...IN_RSLT_PG
and a download copy of win8
http://windows.microsoft.com/en-US/windows/buy
And 16 GB RAM
http://www.newegg.com/Product/Pro...D=10440897

for about $285($255 after rebate) .

This was just a quick search I am sure you can do better if you invest a little more time. I didn't add a video card, but if you need one you could go down to 8 GB RAM
http://www.newegg.com/Product/Pro...D=10440897

and hopefully find a deal on a decent video card.

If you are comfortable building your own computer, it might not bea bad idea. However, remember that there is the cost of the windows license which can be expensive.

I purchased a similar hp computer (pavilion p6-2200z) with an e2-3200 processor and ended up upgrading both the ram and the processor since it did not meet my needs anymore. While I personally got a great deal on the desktop, I now have a spare processor lying around.

The computer you purchased would be more than adequate for basic office work and web browsing, but for more computer intensive tasks, you might need a more powerful computer.

In case you were wondering, I was using my computer as a security system, so the processor started to struggle when I added too many cameras. However, it worked very well for office work.

My 2c:
When you build a cheap computer, you want to start with something that will be upgradeable as soon as you have money (more ram, additional hdd's, a graphics card or two, etc.). That being said, I would stick with 4-8gb of RAM, and pickup an amd a10-5800k cpu/motherboard combo. I had the a8 version of this APU and the onboard graphics were good enough to play older games on high settings (warcraft 3 played on all the highest settings).

Here's a good combo with the A10 and a motherboard with 2 x16 slots (in x16/x4 which means it supports crossfire with 2 amd gpu's, DOES NOT support SLI):
http://www.newegg.com/Product/Com...bo.1146361
That motherboard has 4 ram slots, so IMO pickup a single 4gb stick of ram to start:
http://www.newegg.com/Product/Pro...6820148538
And we're at about $190. That leaves you some room for a windows license and maybe an SSD if you stretch your budge a little (your OP didn't mention you had a HDD).

Later on this year, you can add more RAM (3x4gb for a total of 16gb, or upgrade to an 8gb dimm and do 4x8gb for a total of 32gb), pickup a graphics card (there have been some pretty good deals on the HD 7770 recently - good deal if you can get one for about $100 bucks and you'd see a 300-400% performance increase), add a solid state drive to boot from (you can get a small 60gb for 30-40 if you find a deal), and you've got yourself a pretty decent gaming machine.

Note that this is a 100w processor - if you have a 350w power supply you should be able to overclock the graphics core and squeeze out some more performance. When you add a gpu, probably want to upgrade to a 550w for a single gpu and a 750w if you think you'll crossfire down the road.

Hope this helps.