http://support.microsoft.com/kb/922120 I used this link to get my XP machine to be seen on the Vista full map but I am not sure this is your problem some of the links would not open for me so i do not have all the info I hope the link helps.
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Vista Ultimate 32Bit On:Asus P5K Mobo
Intel C2D E8400 3.00/Xigmatek HDT S1283 /3Gig Ram/ATI HD2600XT 256 PCI Express /550Watt Ps/ Antec P-180B Case
Work in Progress with a little upgrade
http://fvernau.echoes.net/index