Comcast XFINITY → [Connectivity] Connection Problems possible modem/network card?

I have been having problems with my internet connection I couldn't download faster then 150kbs when I usually d/l at around 700-750. So I call comcast they say they'll send a tech out, first day he doesn't show up, second day he calls my wife and says he's not coming cause he says its an issue with my computer not his problem...

I run IPCONFIG and notice my IP is different from the one I have had for 4yrs. I thought that was weird and try all sort of crap. So I end up taking out my Realtek Network card and I put in an older Realtek card, and notice my IP has changed yet again, I am on my 3rd IP address. I try downloading from different sites and I get about the same speeds, but my DSLREPORTS stests are up alittle 1000/360 vs 500/360 of first card.

So next I turn on my onboard nvidia lan card and yet again I get another IP address, but with this one my net connection seems normal, benching at 4000/360(close enough suppost to be 6000/380). This only lasted about an 1hr or two.

My question to any network guru's is.... Is my IP suppost to change with every network card because I've changed cards before with my ORGINAL IP address and it never changed, just wondering if this could be my problem?

I can only download at around 150kbs unless I open up multiple connections to the same server then I can get upto around 500-600kbs, what could my problem be?

When I had my Nvidia network card up and running, after I lost my full speed any website I would try would take me to a Install package for comcast internet, which I downloaded and ran, which allowed me to connect to sites again.

Is this connected with the multiple IP's I have one for each network card... Which unless they changed something I had the same IP for yrs...

To answer your first question yes your ip is suppose to change with each nic since the dhcp server will assign a new ip to each mac it finds contacting it and mac id's are unique to the equipment.
As for your slow speed issue at least part of it may be due to routing so when you change your ip and end up on a different subnet the routing improves. but to look further please review »Comcast High Speed Internet FAQ »How To Get Help!

Thanks for the link

Here is my tweak results - »/tweak ··· a=normal

My speed test results - Last Result: Atlanta Server
Download Speed: 3183 kbps (397.9 KB/sec transfer rate)
Upload Speed: 357 kbps (44.6 KB/sec transfer rate)

Last Result: Chicago Server
Download Speed: 1982 kbps (247.8 KB/sec transfer rate)
Upload Speed: 356 kbps (44.5 KB/sec transfer rate)

If I go by the speedtests at dslreports page I get 500-1000/352. Which would be more precise as to what I am actually seeing.

My modem shows
Frequency 405000000 Hz Locked
Signal to Noise Ratio 33 dB
Power Level -6 dBmV
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading

Upstream Value
Channel ID 2
Frequency 33008000 Hz Ranged
Power Level 47 dBmV

I've tried 3 different nic's so I can rule out that, except for the brief time I had full connection with my nvidia nic.

I have tried calling tech support all day but the line has been busy, and I've had my problem since Wensday Night.

I have also eliminated it as an OS problem by triing the same tests on my second OS on a different HD, same results.

I even tried hooking up the modem using the usb port same ordeal.