Conexant HCF V.90 56K Data/Fax PCI connection & browsing problems, maybe.

I am about tapped out of home-grown remedies and need someone's wisdom and help.  My system is a Dimension 4300, 1.67 GHz, 40 GBHD, 256K RAM, running XP (HE).  My ISP is Earthlink.  I run Earthlink's Total Access 2004.  I uninstalled the Earthlink Accelerator software because I felt that it might have been a contributor to frequent connecting and disconnecting problems.  My connections, browsing and disconnects have been instable and are now mostly just terribly slow.  With or without Accelerator, I connected at about 48.0 Kbps.  In view of the frequent connection problems, on technical support advice, I included the initialization string "+MS=V34" in the connection settings.  With this string, I connect at about 31.2 Kbps.  Recently, I noticed someone mention a string "AT+MS=V34" in conjunction with a Conexant HCF V.90 modem, so maybe I am using an incorrect string.  Before uninstalling Earthlink Accelerator I ran its diagnostics test on the phone line.  The test frequently (but not always) indicated a "bad connection".  Based upon that information and technical support advice, I had the phone company check the line(s) for noice.  Whatever there was, they claim to have fixed, but to little avail.  I wondered whether the problem might reside with the system and therefore ran a Norton System Works 2003 speed test.  The system proved to be working fine.  More recently, I have been focusing on the modem as the principal source of the problem.  I ran the "Modem Helper" utility, which indicated that the modem was working fine and that a "bad phone line connection" might be an issue.  Based upon a message in this forum, I tested the phone line quality pursuant to Dell Knowledge Base Doc. No. H01042823.  I ran the test of both lines, telephone and internet.  The results were almost identical:  Signal-to-Noise Ratio = 35> dB; Symbol Rate = 3200 baud; Carrier Frequency = 1829> Hz.  Based upon that information, it appears that a V.90 modem will have difficulty and instability on these lines.  Meanwhile, everything is as slow as molasses.  Sometimes, it is also slow to release the phone connection, taking almost a minute to let go.  I also removed all phone line splitters, surge protectors, etc., which made no, or almost no, difference in connection speed.   Next to this computer is a Dimension XPS B533r running Win98, Total Access 2004 and Earthlink Accelerator, which uses the same phone line as the subject system.  It has few problems connnecting, browsing, disconnecting, etc. and is reasonably fast.  What do you think?  Is there anything I can do to improve my connection and browsing speed on this system?  Is there a better initialization string?  Was Earthlink Accelerator in fact part of the problem? or would it perhaps help to speed things up?  Would it help to download/install the Conexant HCF V.90 generic PCI driver update for WinXP released 2/25/2004 (available on Conexant's web site)?  Are there any obscure settings (com port, IE, modem, etc.) that might be causing these problems.  I feel this machine should be a race horse instead of a snail.  Any other ideas?  Thanks for your help.