From your description of the problem it sounds like a issue with the network connection (not necessarily the internet, but the actual NIC) and/or the cable.
Some high end video game and video editing machines run from $3,000 to $10,000, and if you are talking professional machines, a whole lot more.
3K-10K is a huge over-estimation; but 550 dollars will generally be relatively low-end. on the other hand- it really depends what his current PC is!
Anyway: the build EEVIAC described:
Motherboard:ASUS P5G43T-M Pro LGA 775 Intel G43 HDMI Micro ATX Intel Motherboard - Retail
CPU: Intel Pentium E6600 3.06GHz 2MB L2 Cache LGA 775 Dual-Core Desktop Processor - Retail
CASE: Black Apex TX Series Micro ATX Tower Computer Case TX-381-C, 90mm Fan, w/o Power Supply
PSU: SeaSonic S12II 380B 380W ATX12V v2.3 80 PLUS BRONZE Certified Active PFC Power Supply - Retail
Graphics: SPARKLE SF-PX84GS512U2-HP Passive GeForce 8400 GS 512MB 64-bit GDDR2 PCI Express x16 HDCP Ready Video Card - Retail
HD:Western Digital Caviar Blue WD800AAJS 80GB 7200 RPM 8MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
DVD:LITE-ON Black 24X DVD+R 8X DVD+RW 12X DVD+R DL 24X DVD-R 6X DVD-RW 12X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache SATA 24X DVD Writer LightScribe Support - Retail
It's important to note that all CPU's come with a heat sink, fan, and thermal grease, and as long as you don't overclock, these will work great. (don't believe ANYBODY who tells you otherwise- it just wouldn't make economic sense for Intel or AMD to sell a CPU with a warranty and then include a heatsink/paste that makes sure people will need that warranty, does it?
I was going to say that some of these components were relatively low on the scale, but then I remembered the 550$ limit, which sort of limits selection I guess
.
No offense intended EEVIAC (it is a good build, I couldn't come up with anything better myself) but it might be a good idea to wait for Patio, I remember Patio and Calum helped shave a good several hundred dollars off my 1,100 dollar or so build, AND the resulting PC was far better, so you never know. Don't know how one could improve EEVIAC's suggestion (aside from using the cost of the heatsink/fan and thermal paste and putting it towards the other components) but then again that's what I thought about mine at the time as well!