need to upgrade

Solution
what is your budget? are you in the uk? there really isn't a recommendable processor to just drop into your existing machine as it is rather dated. you could get a new motherboard and cpu and still use everything else, but without knowing your budget it is hard to say.

PCPartPicker part list / Price breakdown by merchant

CPU: AMD A10-5800K 3.8GHz Quad-Core Processor (£72.62 @ Amazon UK)
Motherboard: Gigabyte GA-F2A88XM-DS2 Micro ATX FM2+ Motherboard (£36.71 @ Ebuyer)
Total: £109.33
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-24 07:34 BST+0100
what is your budget? are you in the uk? there really isn't a recommendable processor to just drop into your existing machine as it is rather dated. you could get a new motherboard and cpu and still use everything else, but without knowing your budget it is hard to say.

PCPartPicker part list / Price breakdown by merchant

CPU: AMD A10-5800K 3.8GHz Quad-Core Processor (£72.62 @ Amazon UK)
Motherboard: Gigabyte GA-F2A88XM-DS2 Micro ATX FM2+ Motherboard (£36.71 @ Ebuyer)
Total: £109.33
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-24 07:34 BST+0100
 
Solution
E2 3200 - 1512 points
Any of these processors is at least 2x faster than your current CPU
A6 3650 - 3199 points
A8 3800 - 3156
A8 3850 -3537

Here , you can see processors of the same socket , but some of them are not listed by HP
http://www.cpu-world.com/Sockets/Socket%20FM1.html

For sure the first three i posted are supported but obviously A8 3850 is rather expensive . If you can find somewhere one of the three i posted for less , it would do the job .

http://www.cpubenchmark.net/cpu_list.php
 
well you can defintely go the intel route and maybe save a little money...

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Pentium G3240 3.1GHz Dual-Core Processor (£38.67 @ Amazon UK)
Motherboard: MSI H81M-P33 Micro ATX LGA1150 Motherboard (£30.97 @ Scan.co.uk)
Total: £69.64
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-24 08:37 BST+0100

if your never going to do gaming and you are just doing regular web browsing, youtube, office apps, the pentium is just as good. but i feel for long term the 5800k offers so much more definitely in possible gaming or home theater work down the road and is slightly faster overall.