First thing to do is run both download and upload tests here and post the results, that way we can get an idea of the speeds you are getting currently. Bittorrent is not a good way to measure speed as it's dependent on the speed of who you are downloading from.

MTU = 1446
MTU is not fully optimized for broadband. Consider increasing your MTU to 1500 for better throughput. If you are using a router, it could be limiting your MTU regardless of Registry settings.
MSS = 1406
MSS is not optimized for broadband. Consider increasing your MTU value.
 
Default Receive Window (RWIN) = 1045440
RWIN Scaling (RFC1323) = 4 bits (scale factor of
Unscaled Receive Window = 65340

For optimum performance, consider changing RWIN to a multiple of MSS.
Other values for RWIN that might work well with your current MTU/MSS:
517408 (MSS x 46 * scale factor of
258704 (MSS x 46 * scale factor of 4)
129352 (MSS x 46 * scale factor of 2)
 64676 (MSS x 46) 
bandwidth * delay product (Note this is not a speed test):

Your RcvWindow limits you to: 41817.6 Kbps (5227.2 KBytes/s) @ 200ms
Your RcvWindow limits you to: 16727.04 Kbps (2090.88 KBytes/s) @ 500ms
MTU Discovery (RFC1191) = OFF
Time to live left = 56 hops

TTL value is ok.
Timestamps (RFC1323) = OFF
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349) = 00000000 (0)




The current date is: Sat 12/31/2005
The current time is: 20:32:01.35

Microsoft Windows XP [Version 5.1.2600]


Pinging testmy.net [67.18.179.85] with 32 bytes of data:



Reply from 67.18.179.85: bytes=32 time=118ms TTL=48

Reply from 67.18.179.85: bytes=32 time=59ms TTL=48

Reply from 67.18.179.85: bytes=32 time=60ms TTL=48

Reply from 67.18.179.85: bytes=32 time=60ms TTL=48



Ping statistics for 67.18.179.85:

    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

    Minimum = 59ms, Maximum = 118ms, Average = 74ms

 
Ping Complete.
 
 


Tracing route to testmy.net [67.18.179.85]

over a maximum of 30 hops:



  1    19 ms    26 ms    17 ms  bras9-l0.pltnca.sbcglobal.net [151.164.184.65]

  2    14 ms    15 ms    14 ms  dist1-vlan50.pltn13.pbi.net [64.164.97.66]

  3    14 ms    15 ms    13 ms  bb1-10g2-0.pltnca.sbcglobal.net [151.164.42.100]

  4    14 ms    15 ms    15 ms  bb1-p4-0.crsfca.sbcglobal.net [151.164.41.5]

  5    17 ms    16 ms    15 ms  ex1-p14-0.eqsjca.sbcglobal.net [151.164.41.10]

  6    79 ms   162 ms    92 ms  bpr2-ge-6-0-0.SanJoseEquinix.savvis.net [151.164.89.42]

  7    17 ms    18 ms    18 ms  dcr2-so-3-2-0.SanFranciscosfo.savvis.net [206.24.211.77]

  8    30 ms    31 ms    32 ms  dcr1-so-2-0-0.LosAngeles.savvis.net [204.70.192.89]

  9   122 ms    65 ms    64 ms  bcs2-so-1-3-0.dallas.savvis.net [204.70.192.250]

 10    64 ms    61 ms    61 ms  bcs1-so-6-0-0.Dallas.savvis.net [204.70.192.49]

 11    61 ms    61 ms    62 ms  dpr1-as0-0.dallasequinix.savvis.net [204.70.193.214]

 12    63 ms    62 ms    62 ms  aer1-po10.DallasEquinix.savvis.net [204.70.134.14]

 13    58 ms    58 ms    57 ms  208.175.175.42

 14    58 ms    58 ms    58 ms  vl31.dsr02.dllstx3.theplanet.com [70.85.127.30]

 15    59 ms    60 ms    59 ms  vl41.dsr01.dllstx4.theplanet.com [70.85.127.83]

 16    59 ms    61 ms    59 ms  gi1-0-2.car17.dllstx4.theplanet.com [67.18.116.85]

 17    60 ms    61 ms    63 ms  85.67-18-179.reverse.theplanet.com [67.18.179.85]



Trace complete.

Your connection is: 381 Kbps      (about 0.4 Mbps)
You downloaded at: 47 kB/s
Your TRuSPEED: ^info^ 408 Kbps :: 50 kB/s (7% overhead factored)
Bottom Line: You are running: 7 times faster than 56K and can download 1 megabyte in 21.79 second(s) 
Diagnosis: May need help : running at only 21.25 % of your hosts average (pacbell.net) 






Your connection is: 217 Kbps      (about 0.2 Mbps)
You uploaded at: 26 kB/s
Your TRuSPEED: ^info^ 232 Kbps :: 28 kB/s (7% overhead factored)
Bottom Line: You are running: 4 times faster than 56K and can upload 1 megabyte in 39.38 second(s) 
Diagnosis: May need help : running at only 80.07 % of your hosts average (pacbell.net) 



im not sure which cablenut file i used

after using the attached cablenut setting file the results are:


Your connection is: 353 Kbps      (about 0.4 Mbps)
You downloaded at: 43 kB/s
Your TRuSPEED: ^info^ 378 Kbps :: 46 kB/s (7% overhead factored)
Bottom Line: You are running: 6 times faster than 56K and can download 1 megabyte in 23.81 second(s) 
Diagnosis: May need help : running at only 19.69 % of your hosts average (pacbell.net) 

You may have picked up something nasty in a download.  Have you scanned for spyware and malware?  The STICKY provides some great free programs which will help you clean your system, I would suggest trying them.

This one has me confused. I tested the cablenut file I posted with my own connection and it will even support up to a 15 Mbps/2 mb connection, at just over 14300 Kbps. So there is definitely a hardwarde problem. When was the last time you reset your modem? if it's been a while you should do so and try testing again.

OK dumb question are you connected to your modem by ethernet cable or USB?  The way it's acting I'd almost think there is a 384/256 cap set on your connection. you might want to call your provider and have them check you modem's provisioning and  make sure it's set to what level you pay for.