[dds.scr and dds.com won't run on Win XP 64 bit Pro]

This is my first post in the forum. I have relied on Malwarebytes many times to solve any suspected infection issues.

One of my PCs runs Win XP Pro 64-bit. I read the instructions in this forum & downloaded dds.scr and dds.com. Neither will run.

An initial MB scan previously detected the following:

Malwarebytes Anti-Malware 1.65.1.1000

www.malwarebytes.org

Database version: v2012.11.24.02

Windows XP Service Pack 2 x64 NTFS

Internet Explorer 8.0.6001.18702

Administrator :: OPTERON175 [administrator]

11/23/2012 11:10:54 PM

mbam-log-2012-11-23 (23-10-54).txt

Scan type: Full scan (F:\|)

Scan options enabled: Memory | Startup | Registry | File System | Heuristics/Extra | Heuristics/Shuriken | PUP | PUM

Scan options disabled: P2P

Objects scanned: 267905

Time elapsed: 32 minute(s), 36 second(s)

Memory Processes Detected: 0

(No malicious items detected)

Memory Modules Detected: 0

(No malicious items detected)

Registry Keys Detected: 0

(No malicious items detected)

Registry Values Detected: 1

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run|Regedit32 (Trojan.Agent) -> Data: F:\WINDOWS\SysWow64\regedit.exe -> Quarantined and deleted successfully.

Registry Data Items Detected: 0

(No malicious items detected)

Folders Detected: 0

(No malicious items detected)

Files Detected: 1

F:\WINDOWS\SysWOW64\regedit.exe (Trojan.Agent) -> Delete on reboot.

(end)

They were successfully deleted & a follow-up scan found no threats.

Two days later I ran another scan & it found the same items, which again were deleted.

I'm not sure why it is reoccurring. That is why I tried the two dds files, but they can't help. Is this serious? I have noticed constant network activity on this PC even when no browser or email program is open. I disabled the network card until I can find out what is causing this.

Thanks.