I finally found a Tcp-Ip patch for XP64 SP2 which I've been looking for a while, so I thought I'd share it with you 
rar file with four versions - 50, 100, 200 and 1000 half-open connections limit:
http://rapidshare.com/files/38217392/4226_Fix.rar.html
If you would rather have it gone completely, here's a file with the limit at 16.7M (highest possible number):
http://rapidshare.com/files/23629463...tcpip.zip.html
Do-It-Yourself instructions: (65k limit in below example)
Found all this from a link to a PlanetAmd64 thread:
http://www.planetamd64.com/index.php...ic=31013&st=20

-hexed by zork on 3.29.07 because no one has bothered making a patch to fix 4226 on Windows XP Pro x64 sp2
-based on version 5.2.3790.3959
-half-open connections limit is returned to 16,777,215
-released on demonoid.com.
install for dummies:
1. boot into safe mode
2. FIND file (win+f) tcpip.sys
3. delete all instances of it for your XPx64 installion except the one in this directory
4. copy the tcpip.sys in this dir to c:\windows\system32\drivers (or whatever your install dir is)
5. if SFC whines, press 'cancel' then 'keep new'
6. reboot
-based on version 5.2.3790.3959
-half-open connections limit is returned to 16,777,215
-released on demonoid.com.
install for dummies:
1. boot into safe mode
2. FIND file (win+f) tcpip.sys
3. delete all instances of it for your XPx64 installion except the one in this directory
4. copy the tcpip.sys in this dir to c:\windows\system32\drivers (or whatever your install dir is)
5. if SFC whines, press 'cancel' then 'keep new'
6. reboot
http://rapidshare.com/files/38217392/4226_Fix.rar.html
If you would rather have it gone completely, here's a file with the limit at 16.7M (highest possible number):
http://rapidshare.com/files/23629463...tcpip.zip.html
Do-It-Yourself instructions: (65k limit in below example)
TCPIP.SYS 5.2.3790.3959
Hex (Offset) Mod Original
00000148 1B 26
00000149 7E 7D
000B85CC FF 0A
000B85CD FF 00
000B85CE FF 00
The first two (148 & 149) are the checksum of the file, the others are the limit.
If you want to use a smaller limit, you need to calculate the correct checksum again, I use pechksum to calculate it. edit it & replace it in Safe Mode.
Hex (Offset) Mod Original
00000148 1B 26
00000149 7E 7D
000B85CC FF 0A
000B85CD FF 00
000B85CE FF 00
The first two (148 & 149) are the checksum of the file, the others are the limit.
If you want to use a smaller limit, you need to calculate the correct checksum again, I use pechksum to calculate it. edit it & replace it in Safe Mode.
http://www.planetamd64.com/index.php...ic=31013&st=20