I have an old coputer (Pentium 4 at 1.8) in which I have maxed the RAM at 1GB-
I have on-board video-
I was looking into getting a PCI video card with maybe 256 or 128 mb of memory-
mY question

Would It make a difference in term of speeing up web browsing, video playback and streaming.

I don't play any games on this computer-

Another words is a worth the 30-50

Thanks for your help

Niot really, no.

It won't really speed up the internet browsing, It may help the frame rate when you are streaming videos and make them run a little smoother though. It would be worth $50

no regarding the pci video device- save your money , your system will have onboard AGP video device that is manually configurable via BIOS setup ,
(DEL or F2 or F10 at system power up - consult the first display - can click pause button to freeze display)

Typically for system era, from 8MB default up to 256MB
Under video memory and/or aperture setting in advanced

WinXP sp3 uses about 400MB ram memory for internet and internet related tasks - so minus windows preferred 30% freespace using 1GB installed ram memory leaves up to 128MB you can comfortably configure for , if supported.
Changing say 8MB to 128MB will be noticeable when changing pages - but a connection with burst dl speed over 100KB/s will help.

Also update java runtime and adobe flash player for best quality internet experience.

Your probable onboard ATA100 ide host bus adapter connected to a likely slow oem ide hdd will be the big bottleneck for internet related performance (burst speed for page changing and sustained speed for security scans)
so maybe investigate a faster hard disk drive sub-system

Aslo check the system vendor or mainboard vendor or chipset vendor for chipset/video related uogardes and/or config utilities
regards from tbright

HP evo D510 1.8GHz/512MB/8MB.64MB onboard video/10K scsi drive
oem winXP sp3, explorer8