The steps are for increasing BROADBAND speed in Windows XP and also work for 56k modems too.
1. Logged on to computer using Administrator Credentials.
2. Start > Run > type “gpedit.msc” (It is not available in XP Home)
3. Expand the Local Computer Policy.
4. Expand the Administrative Templates.
5. Expand the Network branch.
6. Highlight the “QoS Packet Scheduler” in left side window.
7. In right Window double click the “limit reservable bandwidth” setting.
8. On setting tab check the ENABLED item.
9. Change the value to 0 (ZERO), where it says “Bandwidth limit %” .
10. Close gpedit.msc.
11. Restart the system and check with the network connection speed. Note: It does not work on XP Home Edition.