RAM Upgrade & Compatibility

[crazy_yossarian]

Motherboard: Intel 845GVSR
Slots: 2
Free: 1
Current RAM: DDR 256 MB PC266 MHz
OS: Win XP

Want to add 512 MB to the 256 MB.

Following are my queries:
1) Compatible RAM speeds with the motherboard?
2) Will using RAM of higher speed alongwith the existing 266MHz speed RAM harm the motherboard?
3) What does backward compatible mean? If it means that higher speed RAM can be used with an older lower speed RAM, then which speed will the combination work at?

Please help me.
Regards,
Yossi

[Disk_Contented]

General
MPN: KD845GVSRPAK10, BOXD845GVSR, BLKD845GVSR, D845GVSR

Product Type: Motherboard

Form Factor: Micro ATX

Width: 23.4 cm

Depth: 20.8 cm

Compatible Processors: Celeron, Pentium 4, Celeron, Pentium 4, Celeron D <<<<<<<<<

Processor Socket: Socket 478

Chipset Type: Intel 845GV

Max Bus Speed: 533 MHz

BIOS Type: AMI

Storage Controller: ATA-100

Max Processor Speed: 3.06 GHz

Memory
Supported RAM Technology: DDR SDRAM

RAM Installed ( Max ): 0 MB / 2 GB (max) <<<<<<

Supported RAM Speed: PC2100, PC1600, PC2700 <<<<<<<<<<<

RAM Features: Unbuffered

Video
Graphics Controller: AGP - Intel Extreme Graphics, Intel Extreme Graphics, AGP 4x - Intel Extreme Graphics

Video Memory: Shared Video Memory (UMA)

Audio
Audio Output: Sound card

Signal Processor: Intel 845GV

Sound Output Mode: Stereo

Compliant Standards: AC '97

Audio Codec: Realtek ALC202A

The board will run 333 memory, but it depends on the CPU