Hi hari_seldon99,
Maybe I can help a little as I also have a Compaq Desktop Pro only it is ~700 mhz

126meg me 16 gig hd PVR-150
Ok with the rf modulator, I got mine at Kmart ~$25 +tax of course. Works well and has three ports in. However, I am not using it on the pvr-150 (not an option) but do use it on my "production" machine with the 350.
The getting tv out of the 350 is a bit touchy. One of your best tools is the ssh and come in from a different box. Take it in two steps, tv out first then the desktop out on tv also. The latter can be a pain.
By using the remote shell, as root, you can play with the xserver settings to get things going. First you do a "killall gdm". Go in and do your edits in the XF86Config-4 file, I think there are a couple of sample files you can build from. Make a backup copy of what you have as there will be information that you will require. Like the video drive, mine uses the mga.
The key is as a remote login, you can do a "startx" and watch the error messages. When all is well, it may complain about fonts and things however it won't return to the cmd prompt. You have to do cntrol C to terminate, however at this point you can do "gdm" and bring the system backup up. There is also a check box in the tv settings to enable tv out from the pvr-350.
The Bus ID doesn't come into play until you get ready to send to the tv however the frame buffer is needed. You may not need to make the vga=normal in the lilo, unfortunetly, I can't say for sure. End result is when you play tv or a recording, the computer screen will go black nd the tv should output via the modulator. Us a recording for testing as it takes the cache out of the equation.
At least this may give you a bit of an insite?
parts of XF86 file... This is the meat of my XF86Config file using a pvr-350
#6June2005
Section "ServerLayout"
Identifier "XFree86 Configured"
# Screen 0 "TV Screen" #everything to tv
Screen 0 "Screen0" 0 0 #tv out only
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "PS/2 Mouse" "CorePointer"
...................
Section "Device"
Identifier "Hauppauge PVR 350 iTVC15 Framebuffer"
Driver "ivtvdev"
### change fb1 to whatever number you got in the previous section
Option "fbdev" "/dev/fb1"
Option "ivtv" "/dev/fb1"
### change the busid to whatever is reported by lspci. Note that
### output of lspci is hex, so add a preceding "0x" to the BusID
BusID "0:9:0"
EndSection
................................................
Section "Screen"
Identifier "TV Screen"
Device "Hauppauge PVR 350 iTVC15 Framebuffer"
Monitor "NTSC Monitor"
DefaultDepth 24
DefaultFbbpp 32
Subsection "Display"
Depth 24
FbBpp 32
Modes "720x480"
EndSubsection
EndSection
A potential area of trouble is with the audio, the Compaq uses snd_es1688 which is discovered properly with "alsaconf" "alsamixer " sets the values for output. Audio from the 350 is a fixed level and not controlled by the F10 - F11 anyway.
If this doesn't help, maybe I can dig up some more tomorrow
Mike