Remote PC Access

Ok, so my dad needs some help with some Remote PC Access problems. Here are the specs.

Software: GoToMyPC
Connection Type: PC1 - DSL, PC2 - Broadband
Firewalls: PC1 - ServicePack, PC2 - AVG Antivirus
OS: PC1 - XP, PC2 - Vista

Problem: Everything works, but the connection/software from both PCs is slow, especially the file transfer.

Question: I am wondering if this has to do with the fact that there are two types of connections. Is there any remote PC access software (license of course) that is made for handling two connections, and at the same time is fast?

I am also wondering if the connections even have anything to do with this.

Some Extra Info: PC1 - is at a buisness, PC2 - is at a residence
ISPs: PC1 - SBC Yahoo DSL (TM), PC2 - Insight Broadband (TM)

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He did use the software that came with his Terabite network server but that was about the same speed of GoToMyPC

ALSO: This is a MioNet (TM)

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Any help would be great!