Cant help you with drivers but can shed some light on upgrade options... I have the Inspiron 4150 (see sig) which is exactly the same laptop as the 610/ 640 but where the inspiron was the consumer version and the lattitude was the business version. 610 was PIIIM and 640 was P4-M but otherwise they were the same.
Processor:
Hes got the top model for the 610. (Intel did briefly make a 1.2Ghz PIIIM but I dont think dell ever sold it so would not have the bios support for the 1.2.
Video:
It will take up to the ATI Mobility M7 (Which is the Mobility Radeon 7500c 16 or 32 Meg DDR) which is a daughtercard and can be straight swapped. A recent bios upgrade on the 610 MIGHT support the card, though you would have to source a card off ebay as dell never would sell the daughtercards direct to customers. If you can get an M7 it is about 50 to 100% faster than the '2go' in general.
Ram:
You have 2 memory banks in the C610 (easily accessible), and each will take a 512 stick of PC 133 SDRAM SoDimm. So thats 1024 Meg max.
Drives:
The main drive is hot swappable and is the same as those used in the Lattitude 610/640/810/840, Inspiron 4000/ 4100/ 4150 and the 8000/8100. Your options are (depending on what you can find on ebay or what dell still sell)...
DVD Module (8x)
CD Module (24x)
DVD/CD-RW Combo Module 8x/24x/10x/24x
DVD Rewriter Module (Not sure what speed)
Floppy Drive Module
ZIP 100Mb Module
HDD Module (Takes any 2.5" notebook drive as a 2nd drive)
Second Battery Module
Hard Disk:
Will definately take up to a 40Gb 5400RPM drive (Incredibly easily swappable also) and Ive seen the off C610 using a 60Gb drive without problems. Not sure about 80Gb drives though as the bios may not support those.
Mini PCI:
You have a standard Mini PCI card slot (easily accessible) which will take a Dell truemobile WI-FI card...Can be had for about £30 ($60?) off ebay or less.
Thats about it really, except to say that the vid card can be gently overclocked via software (both the 2go and M7) which makes a subtle difference in games....Oh and the 5400RPM drive makes a HUGE speed difference on the lattitude/ Inspiron over the standard 4200RPM...Believe Me!
Si
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Current system:
Dell Inspiron 4150XT
1.9 P4-M
512Mb DDR2100
40Gig Hitachi 5400RPM
32Mb DDR Radeon M7 (7500c)
14" SXGA+
Hot swap DVD/CD-RW Combo Module
Hot swap FDD Module
Hot swap CD Module
Dell Truemobile Wireless
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On Order....
Systemax 5202
2.0 P-M Dothan
512Mb DDR2700
60Gig HDD (Crappy 4200)
128Mb DDR Radeon M11 (9700)
15" SXGA+
DVD+R/RW Drive
Intel Centrino Wireless
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