Enable psexec access on Windows XP machine

Add this registry value :
reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\system /v LocalAccountTokenFilterPolicy /t REG_DWORD /d 1 /f

Disable firewall (if firewall active) :
 netsh advfirewall set allprofiles state off

If the current user doesn't have password (blank password) :
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa] "LimitBlankPasswordUse"=dword:00000000

Using Local Policy editor :
Start -> Run -> secpol.msc -> Local Policies -> Security Options -> Network Access: Sharing >and security model for local accounts -> Classic – local users authenticate as themselves
if already in 'Classic':
move to "Guest only - .." run from elevated command prompt gpupdate \force move back to 'Classic - .." again run from elevated command prompt gpupdate \force

You can try the command

net use \\computername\ipc$ /user:adminname password

to get admin permissions on remote PC before use psexec.